I'm not trying to convert anyone to loving Ranma 1/2 or the like.  I am just 
trying to give you the idea that Ranma characters are easily molded to the 
writers imagination.  Thusly, it is easier to write for Ranma, than lets say 
DragonBall Z or Street Fighter.  Also, Ranma can be considered a melting pot 
of all the other series, thusly, a crossover with them isn't too far fetched. 
 And above all, Fanfiction is for both the Writers and the Readers.  The 
writers write for the sake of writing, they aren't getting money for these 
stories and hopefully they increase their skills.  Readers read so that they 
have some stories to enjoy that they don't have to pay for.  If they wish not 
to read Ranma fanfics, or a Tenchi Muyo fanfic, then they have the right not 
to.  No one frces anyone to watch the Animes or Magnas and the writer's 
opinions are their own.  If you don't like it, I guess you'd have to say your 
piece and if they continue, it is their buisness.  Fanfiction is, and I 
repeat, not an industry and thusly do not have to adhear to the reader's 
wishes.