A possibility would involve Akane. I know people dilike screwing
around with  the Akane who is actually almost normal in the Ranma
world. But what would happen if  Akane assidently was hit by the Water
of the Drowned-man and permanently became a man.  Would Ranma
take a female form to be with Akane? This could lead  to an interesting 
post-series based on the development of onna-Ranma, and could involve
Ranma pregnant by  Akane. Bizarre twist, huh?
<<<<<<<<<<<<<<<

This story's been done.  Well, not the pregnancy part, but the
permanenty  male-Akane/female-Ranma has been done.  I forget who did
it or the name of the story, but its on (or was) ftp.std.com.  However,
someone could probably redo it better...