rewind gone nuts has a Ranma/One Piece crossover going, now at four chapters. I think thus far it's just a bunch of the Ranma cast in the OP world -- no actual interaction yet with any canon OP characters. Though that may happen in future chapters.
It seems readable enough. Agree or disagree, I don't really care. But here you are, a link to ch1
https://www.fanfiction.net/s/13725132/1/Voyages-of-the-Wild-Sea-Horse
It seems readable enough. Agree or disagree, I don't really care. But here you are, a link to ch1
https://www.fanfiction.net/s/13725132/1/Voyages-of-the-Wild-Sea-Horse