Ehhh...  there is a bunch that go into this, though admittedly there are more that are Love Hina based on this concept.
The main issue is a lot of the examples to immediately come to mind are notoriously hard to find these days.
I'm not going to list a bunch, here are a few examples:
'Ranma Aijou and Aitou' by JohnnyG did this.  Ranma got the engagement moved to Kasumi and she had to help him thoguh this as he tended to flich or worry she was going to hit him like the rest.  Though JohnnyG deleted his copy and it went to Driver jim ohki, whom deleted his copy and it went to somone else, whom renamed it and did not post it all.
'Relatively Absent' by Togashi Gaijin did this in a completely different way.  Ranmas family ended up rescuing him from the herb arc...   at one point he/she was taking a shower and one walked in on Ranma...  Ranma was fully expecting to be hit and the person whom walked in was horrified...   The family discussed it separate from Ranma and agreed to try to help Ranma through it.   Regrettibly this story was erased fromt he Net, no known valid links to it...
'Nameless Face' by NiteSkyStar covered this from a completely different angle.  Nabiki seriously worried about the healthiness of the relationship between Ranma and Akane actually goes to the Police station to file abuse charges against Akane...  at first the police are reluctant to even hear her out...  they end up up sending in one agent to evaluate the situation...  Sadly never went too much beyond the initial setup and removed from the internet years ago though.
'One Straw' by Porthos112 is a more general thing...  the constant abuse from all sides and the fact Ranma is treated more as a prize instead of a loved one has him retreating to the U.S. and suffering from Combat Fatigue where the FBI in the end decides it is better to help him than attempt to refuse him entry into the country.
'Ranma Baby' by JeremyGU is actually stil available on the net...   Ranma has some initial reluctance to physical contact when nabiki takes over the relationship for real...
'Shared Life' by Innortal it is only touched on briefly...   Kasumi/Nabiki/Ranma share a sould bond after a demon nearly kills the 2 Tendo sisters.
'The Plan' by Tonbo is not exactly what you are looking for, but Ranma was looking to improve his interpersonal skills enough to get out of abusive situations with Akane...  there is a alternative ending where he ends up with Nabiki instead.
R-SM 'Mirrors Reflected' by Metroanime has Ranmas trust in females being destroyed a few times...  normally with him classing them as either violent chicks, or just ones that refuse to return his trust...   he eventually is alone and left open to corruption by the forces of the Dark Kingdom.
R-AA 'Master's Way with Nabiki' by N F R is technically an adult thread on the AA...  but it also is an interesting take on Ranma trying to understand how females think and attempting to date Nabiki using knowledge he gains...   one thing to come out is she discovers he has been conditioned by all the abuse to not respond to genuine affection...   they discuss workarounds.
There are more out there...  but I'm not going to list any more..   Here are some of the links to the above.  Note a couple of these have adult or graphic content...
RANMA 'One Straw' by Porthos112 - [Dld Date=09/06/2007] - [Dld Size=217kb] - [Dld Files=5] - [Status=Inactive]
RANMA 'Ranma Baby' by JeremyGU - [Dld Date=10/27/2012] - [Dld Size=176kb] - [Dld Files=6] - [Status=Not Complete]
RANMA 'Shared Life' by Innortal - [Dld Date=03/11/2006] - [Dld Size=153kb] - [Dld Files=8] - [Status=Inactive]
RANMA 'The Plan' by Tonbo - [Dld Date=10/19/2001] - [Dld Size=259kb] - [Dld Files=3] - [Status=Complete]
R-SM 'Mirrors Reflected' by Metroanime - [Dld Date=05/21/2001] - [Dld Size=200kb] - [Dld Files=2] - [Status=Inactive]
R-AA 'Master's Way with Nabiki' by N F R - [Notice=Graphic Material] - [Dld Date=08/29/2005] - [Dld Size=40kb] - [Dld Files=2] - [Status=Inactive]