There are more then 4 conferences. Some conference winners would be hard pressed to finish last in some other conferences. Supposedly the idea for the Championship is the 4 BEST teams in the country not 4 of the winning conference champs.
best teams win the most games and win their respective division/conference. Like the NFL, an 8-8 team can win in the playoffs and even the championship but they have to get there first by winning their division.
Get the human rankings out of it. nobody wants to see two-three SEC teams duking it out in the playoffs while a few other undefeated teams play in the meaningless bowl games, except us SEC fans.(Meaningless= no shot at a title)