I think that it's best to leave the readers' imagination run off with the
details of Kuno & Nabiki.

As for the TIL aftermath story.. It would cool to see..
Maybe have Ranma come & help her out (he did offer at the end of TIL, yes?),
and meet the mysterious 'destiny' Mousee spoke of.. and maybe a cure for
Ranma.
-However- TIL was wrapped up so nicely, I don't know if I could favor an
epilogue story unless it was done really well..

My opinion (for what it's worth).. Go for the new story.

It doesnt have to tie in as a 'pre-TIL' story (That's what you lead me to
believe). But it does sound like fun.

Paul the Hentai  ;)