Much as I hate to go digging up anything buried on the first page, I've actually got an idea for a workable R 1/2--Highlander cross; the problem here isn't that no matchup works, but that people are so focused on Ranma (which at a Fukufic site isn't surprising, but that's at the moment neither here nor there)
Ranma's a lot of things, but Immortal doesn't seem one of them...he's just too spammed tough to die in the first place, and remember, it takes that to become Immortal. On the other hand, Akane's not only proven mortal, but remember how things go while she's in her doll-form during the final battle with Saffron--her eyes close, and indeed it's a shock that she revives once returned to normal.
What if that wasn't the first time she'd been taken to the point of death? Until the entire site was flooded out, there existed a Spring of Akane--and remember, the other springs were always referred to as "Spring of Drown x-and-such". Considering that Immortals become such after a violent death, what if Akane's immersion really was long enough to kill her? I know it shifts the main character something awful, but it also returns the power-level to a point where the Immortals have a chance.
What I'm picturing is that, after the failed wedding, Akane is beating up her Ranma dummy when suddenly she's struck by a terrible headache (the first time she's really felt less than perfect in the last several weeks). This, we later learn, was caused by Nick Wolfe walking nearby, and eventually he pinpoints this new Immortal, confronts her, and explains to her just what she's involved in.
Of course, to me, it's mainly a Highlander cross with a little Ranma involvement, but perhaps Akane can keep some of her ties to Nerima (though not to Ranma-as-fiance...this storyline pretty much blows that to smithereens)--mainly through finally learning the Art (since she's now too--resilient--for Ranma to have to worry about perma-killing her). Major later romantic triangle: Nick/Akane/Amanda (I can't believe he'd never go back to her, and as for Nick to Amanda, I think she's the only man she's ever really fallen for--even Duncan). Akane learns to wield a sword to keep her head, other Immortals learn really cool ki tricks so that we don't have the same problem we had with Ranma-as-an-Immortal, and basically, good old-fashioned action-comedy ensues.
I put this idea out to anyone, since even my specialty of dialogue has currently deserted me, and even in good times, I couldn't plot a Webcomic, let alone a full-on fanfic...[/quote]