Borrow the NFL conference playoff style. Take the top 6 in the BCS rankings and give the top 2 teams byes. This would satisfy the argument that a playoff would cheapen the regular season. Having a bye in the 1st round of a playoff while 4 of the other 5 teams have to play would be HUGE.
I'm also in favor of either making every conference play a conference title game, or doing away with them altogether. If you do away with the conference title games (and I know they won't, too much $$$), that gives you an extra week for the playoff.
A playoff, sadly, is a pipe dream for D1 college ball though. It all boils down to money, so as long as no one is able to convince the large-conference NCAA presidents to start hating money, it will never happen. And it's a shame.