My sga_genficathon story (
Wraith-Blasting with the Stars, corrected slightly
here) was the first AU I've ever created (I've written in the M7 ATF AU, but that doesn't really count). And... well, once I bagged trying to explain how Teyla got to the theatre, it wasn't super-hard to write, though it was a bit of a trick trying to keep track of who knew what when.
The hard part was, there were things I wanted Teyla and Ronon especially to do which I couldn't have them do, based on canon precedent; and places where they had to do certain things to match canon that didn't really fit really well into the story. In particular, I had to have Ronon collapse twice, to match what happened to him in "Runner" and "Sateda", and it just felt awkward.
So now I want to write Teyla et al. adventuring on Earth. But... I'm not sure I want it to be TEYLA et al. adventuring on Earth. Just, their general type, but with differences, some large, some small. Learning things that maybe our SGA friends wouldn't care about. Or - something.
I've always said that I don't want to write original fic. Don't want to write fic that nobody else would read. Don't want to develop original characters more than is absolutely necessary. REALLY don't want to be a published fic author when I grow up. (There's enough nonfic out there with my name on it, I say modestly.)
OTOH, I'm feeling really unmotivated fic-wise right now - not blocked, just nothing has come up that seems worth the energy.
OTOOH, maybe I could just take my AU characters, twiddle further as needed, and
work my hc_bingo card...