I'm in favor of a 16 team playoff. There are 10 FBS conferences in the nation, so each conference champion gets in. That way every team technically has something to play for. It's what the do in college basketball and it couldn't have worked out better. Sure the little guys will be underdogs, but will also provide memorable upsets along the way. The other 6 spots are at-large selections which would go to a committee.
I think that approach would protect the integrity of the regular season, since most teams won't have a shot of getting in without winning their conference.