An eight-team playoff would result in exactly one extra game for four teams and two extra for two teams, since all obviously would be bowl teams anyway. Division II currently plays a 28-team playoff, and far fewer of those players are on scholarship.
I like an 8 team playoff with first round the week after championship weekend . The first round games would be played at the home field of the higher seed, then proceed with today's format. This would make an occasional southern team deal with northern weather