You most certainly can. A playoff would make the regular season much more meaningful.
If all the "BCS" conferences added enough teams to have championship game then all the conference champions would then advance to a playoff.
That would truly make the regular season a "playoff" from game one.
As it stands the regular season is still influenced by voters, which is absurd, and the bowl selection is much more influenced by which teams can produce the most money rather than which teams had the best seasons.
Again damned if you do damned if you don't, it wouldn't work anyways unless EVERY team would join a conference. if you go by just conference champions than a team like ND would never have a chance at the championship and we all know they would fight tooth and nail just so they don't have to join a conefrence. like I said I understand that people hate the way it's set up (i don't mind it but do agree that there needs to be fewer bowls) but it would be harder than people seem to understand to set up a playoff system in which everyone is happy