Well, I've come up with another possible backstory to get Ranma into the marvel universe. Ranma is actually not Genma's son, Nodoka just married Genma to retain her social status and duped Genma into thinking Ranma is his son, this is also why Nodoka lets Genma get away with so much, she can't let him suspect Ranma isn't really his son.
Ranma's real father is Tony Stark. Nodoka had been a 'companion' for hire to go to nice dinners and such, basically a girl to take to a party, and then sleep with afterwards, but her family was on hard times, and she wasn't very professional about it, and got pregnant from Tony. Realizing she was now useless as a companion, she picked the first idiot who she might be able to convince to marry her afterwards who hired her, Genma, who hired Nodoka to come with him to a party held by the Tendo family celebrating Nabiki's birth. At the time, Soun's parents had still been alive, and had been rich and upper class, so Genma and Happosai had to seem well off, and they were given money from Soun to rent stuff and look good and hire companions. Nodoka came back to Genma after that claiming she'd gotten pregnant from him, and he married her without thinking much of it.
Nodoka, however, still bore guilt about Ranma's true ancestry. After the wedding, Nodoka takes a stressed Kasumi out for to a 'ladies night' at a bar to get Kasumi to let out her stress. Nodoka is the one who gets more drunk, however, and accidentally spills to Kasumi that Genma isn't Ranma's father, and that it's really Tony Stark, the rich industrialist, who doesn't know.
Kasumi, by then, had been harboring a deep dislike for Genma, although she kept her dislike secret because he was a guest and her father's friend, but mostly because of the 'mistakes' he'd made when raising Ranma and the harsh training, especially the neko-ken, which Kasumi really wanted to help cure Ranma of by trying to get him used to cats in a non-hostile environment, which was why she brought all those cats to the dojo when she found out, since Kasumi likes cats. Kasumi wants Ranma to be freed of his conflicting obligations and to get Genma out of the house by having her father get mad at him from Ranma not marrying Akane, so she calls Stark Industries annonymously and explains that she suspects Saotome Ranma is really the son of Tony Stark, and that she believes he's been abused.
While this is happening, Ranma's making new revelations in his training in the martial arts. During the Saffron battle, Ranma realized he'd been using the soul of ice without feeling 'cold'. Cologne, when Ranma asks for her advise about it, explains that with the soul of ice and the moukou takabisha, as well as other techniques, the emotion invested in the spiritual energy is only a shortcut and training method to help visualize and focus the spiritual energy into the form you want it. She explains furthur that there is no real difference between magical spells and martial arts techniques besides the training methods used. The Hiryuu Shoten Ha isn't really about cold and hot air, because the air of a 'hot' battle aura isn't really hot enough to create that sort of tornado, although Ranma's own soul of ice is physically cold enough to create tornados off real heat, but the real objective is to train the user to create spiritual energy that opposes that of their opponent's, to create a storm of spiritual energy, rather than actual hot and cold, which works even if the opponent isn't using hot or cold spiritual energy, and also to learn the control to power up their aura without creating the 'hot' energy. Cologne has him train to use the Moukou Takabisha without the confidence focus, only focusing on the 'weight and substance' he is adding to the spiritual energy, or on giving the spiritual energy 'force and velocity', which is a bit more efficient. She teaches him that the Amaguriken is not a technique, but a level of speed, and the objective of the training is to teach the user to manipulate their spiritual energy to protect them from forces like air resistance and g-forces to allow those high speeds, and to boost their speed with spiritual energy, it is a level of speed the human body can't obtain without using spiritual power to boost their abilities. The bakusai tenketsu training is much like that for toughness training, teaching the person to protect themselves with their spiritual energy, something Ranma allready knew how to do from his training with Genma, but has two additional purposes in the destruction of the rocks, you sense the spiritual energy 'frequency' in the rock, and mimic that spiritual energy, shoving it into the rock and overloading it with it's own energy, causing it to shatter for very little expended energy, thus teaching the person to sense and mimic spiritual energy better. Ranma practices and learns the bakusai tenketsu on his own with those explainations, as well as an updated hiryuu shoten ha, by manipulating the spiritual energy around him into opposing swirls to create a hiryuu shoten ha without aid of another fighter, and create more horisontal wind attacks and stuff like that, and also learns emotionless ki blasts, an emotionless ki beam, to make a stronger battle aura, and to create even colder and hotter (physically) auras to burn and freeze stuff. Cologne notes that Ranma's spiritual powers are beginning to breach the generally concieved barriers between magic and martial arts. Happosai decides to get in on the training, because he wants to prove to Ranma that he can teach martial arts, and teaches Ranma a training method to boost his strength to incredible levels with spiritual energy, much like Ryoga (swinging telephone poles), Dr. Tofu (ripping thick books apart with his fingers and tearing a plate apart with his teeth when Kasumi is around), Hinako(carrying lots of people in child form), and Happosai (stopping monster-Taro with one finger) can all already do. And all sorts of hijinx continue to occcur while Ranma is doing all this training, including a new rival who is a mutant (what sort of power?) and lots of dodging fiancees and putting his foot in his mouth.
During this new episode of training for Ranma, Tony Stark has been investigating the 'anonymous' claim, although he was able to figure out it was Kasumi by the recorded voice over the phoen, and finding out about Ranma, the Tendos, and other aquantainces of Ranma in Nerima and elsewhere, and also getting a sample of Ranma's hair DNA tested and researching Genma's past and the training trip. Nabiki, Hinako and Cologne both notice that someone is looking into Ranma, or perhaps someone else in the area's past rather heavily, and Hinako and Cologne tell Ranma about it, while Nabiki sells a lot of information about Ranma and others to the hired investigators, who also go through other channels to confirm the information.
Stark finally comes to Japan to sue for custody, revealing his discovery that he's Ranma's real birth father, but for Kasumi's sake, making it sound like he'd been looking into going to Japan again, and had checked in on Nodoka to see if he could hire her as a companion again to a fancy dinner in the area, and had become suspicious when he discovered her marrige and the time of Ranma's birth, and investigated, and found proof that Ranma was his son, and during the investigation, found out about things like the neko-ken and multiple engagements, and multiple hospitalizations of Ranma from overly harsh training.
Genma is so angry that he was tricked and is now being prosecuted for his many crimes, and Ranma's refusal to run away from the law with him, that he ends up driving Ranma away to the point of agreeing to be adopted by Tony Stark, and Ranma becomes Ranma Stark, with another identity of Lily Stark for the girl form, and a US citezen. Cologne tries to prevent Ranma from leaving and kidnap him and take him to China, as the US is difficult for even the Joketsuzoku Amazons to get into given all the super heroes there, but even though Cologne is able to barely defeat Ranma, she is surprised by the appearance of Iron Man, Stark's alleged bodyguard, who rescues Ranma, although Cologne recognizes Stark by his aura, she's defeated, and Ranma leaves for the US with Stark.
Because of Ranma's curse and lack of English skills, as well as supernatural abilities, Tony sets Ranma up with a few private tutors, one for learning the high scociety Tony is involved with and to not embarras him at buisness dinners or meetings with government figures and stuff like that as well as the fine arts, another to teach Ranma better English and American style living (and ice skating, Ranma finally learns to ice skate properly
), and a third to teach Ranma more academic subjects of math, sciences, and history. Ranma spends most of his free time hanging out at the Avengers Mansion, training, usually with Captain America or Thor teaching him things or as sparring partners. Tony thinks Ranma's too young to be a super hero though, and doesn't want Ranma to be endangered by super villains, so Ranma isn't allowed to go on Avengers missions, something which Ranma heavily resents, especially resenting Iron Man, who is usually the one who is most adamant about Ranma returning home every time he follows the Avengers, although the main reason Ranma doesn't follow them on missions is because the neko-ken makes him terrified of Tigra and even Captain America, while he admits Ranma is powerful and has lots of experience with life threatening situations, is young and should be enjoying his youth and having fun, not bearing the responsibility of saving the world and stuff like that.
Stark finally gets Dr. Strange to come and have a look at Ranma once Ranma's English and academics are good enough to enter a regular American high school. Dr. Strange says that while the Nanniichuan could have cured Ranma before, Ranma's great spiritual development and exposure to pure Jusendo water has powered up the curse beyond the normal powers of the Jusenkyo magic, and demonstrates by retrieving Nanniichuan and using it on Ranma, it only working for a day. He also notes that the curse has healing properties that have been slowly curing Ranma of damage from the years of abuse and malnutrition under Genma, so it's best to leave it in place, and that it's also helping Ranma become more emotionally, spiritually, and mentally mature and balanced, which he needs to be in order to overcome the neko-ken. Dr. Strange explains that the neko-ken is a well of spiritual energy in Ranma which is a cat totem link, like Spiderman's spider totem powers, and that it's really only mental barriers from the trauma of the neko-ken training that are preventing Ranma from using his full cat abilities. Dr. Strange explains that the red hair and eyes in Ranma's girl form are not because of some weird aspect of the cursed magic, but the high levels of spiritual power of the neko-ken being present during the development of Ranma's girl form, combined with a bit of divine heritage from Ranma's mother's side being partially awakened. (decendant of some unnamed god or goddess of Japanese pantheon, Thor notes that this is pretty common and that he'd sensed some immortal blood in Ranma, which was why he was willing to teach Ranma and spar with him, and why Ranma has some superhuman traits beyond regular martial artists) Dr. Strange offers to tutor Ranma in the spiritual arts in exchange for having Ranma work for him as a sort of spiritual troubleshooter for smaller things that need intervention, but don't need Dr. Strange's direct intervention, which Stark reluctantly agrees to after Ranma begs him for the chance to do it and Dr. Strange promises to keep an eye on Ranma and intervene if Ranma really gets in danger.
To allow Ranma to go to school without the curse being discovered by classmates, Dr. Strange creates a necklace for Ranma that temporarily locks Ranma as Lily while Ranma goes to a regular public high school as a junior. Ranma, mostly for practice in spiritual control and to avoid suspicion, has to suppress her aura constantly and limit her abilities to below those of an olympic athelete and hide her levels of martial arts skills, something which Ranma, who is used to showing off, has trouble doing. In the afternoons and on Saturday, Sunday being Ranma's day off, Ranma either trains with Dr. Strange, or goes on missions for Dr. Strange. The missions are stuff like tracking down and slaying vampires, excorsising ghosts from buildings, assisting various super heroes with lesser supernatural problems, and stopping lesser villain or criminal martial artists and spellcasters. Ranma does this with a secret identity(s) of Blue Fist(male form) and Red Fist(female form) wearing a specialized suit designed by Dr. Strage which shifts when Ranma changes form, pretending to be a tag-team pair of super heroes who have one spy on the battle and anyalyze it with stealth while the other fights, because their fighting styles are so similar they'd get in one another's way, supposedly.
Ryoga shows up near the Avengers mansion while the Avengers are gone on a mission, boosted up on MGH, the Mutant Growth Hormone, which has given him Hulk-like levels of strength, toughness, and speed, as well as a controlled teleportation ability, and gets into a fight with Ranma, who he'd been searching for. Ryoga is in a mad rage, and actually proves powerful enough to nearly kill the much more skilled Ranma, who barely defeats him by tricking him into getting splashed before the Avengers get back. Ranma gets a chance to talk to Ryoga before he's taken away to Riker's and finds out that Ryoga blames him for Mr. Tendo being in trouble with the law as well and the Tendos all going into hiding where Akane is upset when Ryoga found her. Ranma contacts Ukyo to find out what has been giong on back in Nerima, since he'd been wondering why he couldn't contact the Tendos, and Ryoga knew the name of the location of Ukyo's new shop, Ukyo reveals that everything fell apart after Ranma left, the Amazons had to go back to China, the Tendos and Saotomes dissapeared and were being searched for by the police, and even the Kuno's were put away thanks to their attempts to buy out the law being out-done by Stark enterprises. Ukyo tells Ranma she's been saving up to go to the US, and learning English, and that she hasn't given up on Ranma, much to Ranma's embarrasment and nervousness, and makes Ranma promise to not loose contact with her, she also says she had to fire Konatsu since he was loosing her more money than he was making, and that he'd been hired by the Hand and had warned Ukyo that the Hand had turned out to be evil ninjas now saught to assasinate Ranma, and some warriors known as Stick and Daredevil, and that Konatsu was staying with the Hand to spy on them and cause them trouble from within their organization.
Ranma gets involved with the whole mess with the Hand and the Chaste, although not as directly as the rest, Ranma comes to help Daredevil and Stick a couple times while they're still in New York, and tells Daredevil how to contact Ukyo and Konatsu when they are going to go to Japan, while Ranma is occasionally dealing with assasination attempts from Hand ninjas, which really ticks off Iron Man, who starts pushing SHEILD to track down and deal with the Hand as well. The Hand's intrest in Ranma turns out to be two fold, one, he has messed up under Dr. Strange's orders, several projects the hand had initiated to gain more influence in New York, and two, they want to kill him and ressurect him as an elite Hand operative.
Through his dealings with the Hand ninjas, Ranma also meets Wolverine, has a fight with Electra, wears an armored suit for a week, before getting frustrated with how it delayed his reflexes, even if it protected him from water.
Blue and Red fist are framed by the Hand, so that Iron Fist goes after them, and Ranma ends up in a long and tough fight with Iron Fist and Power Man, nearly being defeated before being rescued by Dr. Strange, who brings proof that Blue and Red fist were framed.
That's all I've come up with so far...
"Health, Learning & Virtue will ensure your happiness; they will give you a quiet conscience, private esteem & public honor." Thomas Jefferson (1743 - 1826)
