I'm thinking a fic about Rose and asexual 10.5 and their romance would be awesome. And maybe about trying to make babies without sex. I bet 10.5 would want to go all sciency, while Rose would want to keep it simple (turkey baster).

But on the other hand I don't know if I would manage to get through Doctor Who fic. These days I find concentrating on non-Sherlock fics hard.