I've been saying that 8 is the right number, but I could see 12
I think 16 is way too many and renders the regular season less meaningful
If it is 12 you take every conference champ and the best at-large or independent team. However, if I were in charge I'd put stipulations on the conference champ qualifications. To get an auto-bid the conference has to have at least 10 teams, and the champ can have no more than 3 losses.