Actually, the serious idea that came up was about the reason Ranma would run
away, which does happen in Childhood's End.  It seems to me that Ranma and
Akane only grow close to each other because they get placed into situations
where they have to rescue one another, fight for one another, do things for
one another, etc.  It's like the cliche where two people are trapped on a
deserted island and end up falling in love after having to work together doing
things and protecting each other.  Except that it's not a deserted island,
it's a house and dojo.

Or in other words, if there had been 20 Gambling King and Okonomiyaki Sauce
stories, Ranma would be drawn towards Ukyou.  Even if his feelings started
exactly like now.

Ranma might very well want to get away from home in order to avoid that
effect, and really decide on his own without having to be nice specifically
to Akane just because she's the only one living in the same house.

I also _may_ have Ukyou disguising herself as male (like she did before) and
coming with Ranma, though I'm not really sure about this part.