By the way, do you know of a fest that's used the AO3 to release stories over time, instead of all at once?

purimgifts releases them in batches over three days. I'm not entirely sure how roga (the moderator) does it, but I get the impression that she's doing it manually, marking stories for release one at a time. You could PM her and ask; she knows me, so you can tell her I sent you.