4 at large. Let's assume the top 4 is represented as follows:
1. SEC team
2. Pac X team
3. ACC team
4. Big X team
Sugar
SEC vs At large #4
Fiesta
Pac X vs. At large #3
Orange
ACC vs. At large #2
Rose
Big X vs. At large #1
I think you could work out a rotation where two of the bowls get an extra playoff game, one gets the championship, and one gets left out. The one that gets left out gets the championship game the next year. So let's say the Sugar Bowl is the NC game this year (2011). If this was implemented today, in 2012 the Sugar Bowl would only get the "Elite 8" game. No other bowl. In 2013 & 2014 it would get a "Final Four" game, and then in 2015, it would get to have the NC again.