My playoff system would be an 8 team tournament consisting of the big 5 conference champions (SEC, Pac-10, Big 10, Big 12, ACC), plus three at large teams. If implemented this year, and assuming the at large teams would be selected by BCS ranking, the line-up would be:
1) Ohio State (Big Ten Champion)
8) Wake Forest (ACC Champion)
3) Michigan (At Large)
6) Loiusville (At Large)
4) LSU (At Large)
5) USC (Pac-10 Champion)
2) Florida (SEC Champion)
7) Oklahoma (Big 12 Champion)
To preserve the bowl system as much as possible, I'd have the first round take place the week leading up to Christmas, with the games being called the Cotton, Citrus, Peach, and Fiesta Bowls.
The semifinals would take place on New Years, and the championship a week later. The three games would alternate between the Rose, Sugar, and Orange Bowls.