Oh, do I ever hear you! That's why I usually like to just throw something out there, in hopes that plot will develop organically rather than trying to plan stuff out five steps in advance.
This does carry a considerable risk...
Here's one for you:
It's sort of a ghost story--woman loses husband, mourns him for years, and finally meets him again...except that he's been reborn as a woman. The good news is that, er, she has all of his memories. Silliness, drama, and/or havoc ensue, depending on taste.
(I'm already working on this with two other partners, with slight variations. A furry version might be entertaining as well!)