I think that going to a 10/16 model makes a whole lot of sense as a first step, and that above is the best scenario that I can come up with that would be remotely plausible. Notre Dame isn't joining the conference for football, and somehow, in all of this, the concept of athletics beyond football and bsketball needs to be retained.
That's why UMass and Temple make the most sense to complete the second 8 team basketball/olympic division.
Adding Boise, BYU, Airforce, gives those three some kind of natural geographic football scheduling, and solidifies the football side of things with regard to BCS.
In that 10/16 model, there's at least some kind of structure that makes sense competitively and geographically, and at that point, you can start to really pick and choose who to fill out the football side of things, and possibly get to that 12/20 model.
BTW - I don't like the hybrid conference model, but we're apparently stuck with it, so may as well use it as best we can.