Another option would be a six-team playoff, like the NFL's conference playoffs -- the bottom four play in with two games, then the winners play the top two.
If the FBS were only 40-45 teams, I could agree with you. But, with around 60, I think eight is the best number. Playing the first two rounds on campus, like the FCS playoffs do, would place less of a burden on some teams to sell tickets. That would help ensure sellouts, and, make TV people happy.
Now, one change I would make would be that the home team would have to provide 10% of its capacity to the visiting team's fans. So, Alabama (102,000) would have to make 10,200 seats available for a game in Tuscaloosa, FSU (85,000) approximately 8,500, and, so forth and so on.
I also wouldn't be surprised to see some of these games hosted on campus, or in strategically located stadiums, almost like the women's tournament (e.g., putting a Georgia or Georgia Tech in Atlanta, an LSU in the Superdome, a Big Ten team in Detroit or Indianapolis). Basketball tournaments are easy to fill because the stadiums are comparatively smaller, because the teams involved get smaller numbers of tickets (something like 5,000 vs. 15,000), and because each site hosts multiple games.
I believe that the 1st two rounds being hosted by the higher seeded teams would work better. But, meeting at a neutral ground halfway between the two teams is not a bad idea, either.
If the football championship model expects that football fans will travel not only to their conference championship games but also to first-, second- and third-round sites, they'll be sorely mistaken, and a lot of games will look like the fourth quarter of Louisville vs. UConn at The Rent this fall.
