The NFL does it and no one seems to have a problem with it. If there are conferences, then the titles have to mean something. I think having 8 in is a good solution and it only adds one game to the equation. Quarterfinal round is at higher seed's home field with semi's sliding into the existing bowl schedule.
Conference Championships still make the regular season meaningful. You don't have to seed them 1 through 5. You could still have the committee doing the rankings but they would have to get serious about the importance of quality OOC games in the rankings since conference championships would no longer be a factor. For example, if NW won this year, seed them 8 and make them play Alabama at home. You could also have a fall back out,i.e., a team has to be ranked in the Top 12 to be included. It actually makes quality OOC games more viable since you don't have to worry about playing, and losing to, a good team if you can win your conference. You could also have a fall back out, i.e.,a team has to be ranked in the Top 12 to be included.