Why is it always presumed that a playoff has to have 4, 8, 16, etc. teams? I like continuing to stress the importance of the regular season by having rewards aside from being a completely equal member of the playoffs. Byes, home games, etc.
Of course, I generally think trying to have a playoff in college football is dumb. There are too many college football teams and not enough games in the year for there to ever be a truly fair way to whittle the pool down to 1 undisputed champion. Just go back to where everyone does their own thing, you play to win your conference and whatever bowl game that conference is aligned with, and claim whatever you want at the end based on your accomplishments. The free market will judge how much any claim should be recognized.