I can either release it as one double layer disc or two single layer discs... I think I'll do the former, and anyone who wants to split it up can do it on their own prerogative.
At the moment, my plan is to make an eight disc set... one movie per season, and an additional one comprising all the flashbacks (Angel & Darla, Spike & Dru, etc.) and other goodies that didn't make the actual movies. When the whole thing's done, I'll design a cover for an eight-disc case, but for now, someone else has graciously offered to design individual covers (and any other offers are welcome too).
I'm going to work on it sporadically, so it will probably be a long time before the set is finished, but that's the plan.