Then start explaining why you want an expanded playoff instead of simply saying you want one; then I'll ask you why you think two teams isn't enough.
A few years back the Giants won the Super Bowl over the Patriots. The Giants went 10-6 during the regular season; the Patriots went 16-0. Does anybody REALLY think that the Giants had a better season? Be honest; looking at the entire body of work, is there anyone who sincerely believes that the Giants got robbed six times, and the Patriots had a weak schedule, and that their loss in the Super Bowl was anything other than a single bad game?
I prefer to judge a team's season based on an entire season, not on a postseason. Adding more teams to the postseason increases the possibility that a 9-3 team faces an 11-1 team for the championship, when the team that went 12-0 in the regular season loses a single playoff game with no championship to show for it. That, to me, is not a Good Thing.
The problem with your example is the NFL teams tend to play each other more and less cross over.
Take Big 12 vs SEC. The ONLY time those two confesses ever have any hope of playing each other is in bowl games.
It more a play off is need say from the current BCS games. Have the teams that make play off have to make it into one of the BCS games. It would be a much more balance play off system. Right now it all the guess work and a lot of argument over who is the number 1 and 2 with no real play off.