This is just something that i thought of after looking at all of the story
ideas that involve one or more of the ranma cast getting younger. Here's
my contribution. 

What if, for some wierd deus ex machina reason, Nodoka or Genma would wish
that Ranma and Akane could experience the <ahem> "joys" of mirrage.
Following this wish, the two couples have their places switched, with
Ranma and Akane in their 40's and "happily married", and Genma and Nodoka
in their teens and "engaged." It would be sorta funny to see how they deal
with their situations, although the saotome's mirrage seems about as
functional as Ranma and Akane's engagement...

~Eimii