On Sun, 6 Dec 1998 Algerhorn@aol.com wrote:

   Mine may have started out sounding a lot like all of the others but really,
how else can you do it? I mean, he gets split, his female half gets bummed
because she got the short end of the stick, and everyone else is confused and
doesn't know what to make of the whole thing. I'm sure a lot of them start out
that way but that doesn't mean that the direction the story's going to take
will be the same. The idea may have been used before but it would seem to me
like the kind that would always be fun to read about.
   I guess what I really want to know is if I should continue this.

Go ahead and continue it.

There can be multiple fics that use a common fanfic premise, just like there
can be multiple fics that use something that's from the original series.
Nobody says "Oh, no, another fic about a guy who changes into a girl"--the
Ranma premise can support lots of different stories.  A premise that fanfic
writers made up can also support lots of different stories.  Just be careful
that you have a story and that the whole thing isn't _just_ Ranma getting
split into two.