Gary Kleppe wrote:

 "What if Ukyou really *had* been a boy?"

This is easy to do.

Consider an alternate universe where Mr. Kuonji had a son. Desperately
wanting a girl instead, and not being the stable type, he convinced
himself that little Ukyo *was* female, and raised him to believe it.

Well, he hasn't shown up in the US anime or translated manga, but the
character of Konatsu - who, BTW, is also closely linked with Ukyo - was
born male but was raised as a female.  Which doesn't invalidate that
idea, exactly, but...

If Ukyou's really male, there's no reason for him, IMO, to go chasing
after Ranma at all.  He might swear revenge on *Genma*, who is more than
capable of stealing the okonomiyaki cart, betrothal or no betrothal. 
But I doubt it - Ukyo swore revenge on Ranma not because of the theft,
but because she became the object of ridicule, being a girl whose
fiancee ran away.

I think the idea of Ukyo following Genma and Ranma as a student of
Anything-Goes martial arts is the only reasonable one, in which case the
whole character of Ukyo is changed, ne?  No 'Martial Arts Cooking'
skills in AGMA.