I can't speak for cocknfire on this matter, but I agree with every word in Stewart Mandel's latest column. Sometimes two of the nation's four best teams will be in the same conference. I don't think many would argue with that being the case this past season, for instance. Therefore, if college football adopts a four-team playoff, it shouldn't be confined only to conference champions.
In particular, I agree with the final two lines:
"Meanwhile, Bill Hancock and Co. have repeatedly expressed concern about "bracket creep," i.e., the inevitability that a four-team playoff will produce pressure to expand to eight, then 16.
Well, there's one surefire way to make that happen: Stage a four-team playoff that includes the nation's 10th-best team."
Bracket creep is my one big concern about a college football playoff. The temptation to expand the bracket in order to make more money will always be there. However, making sure it only includes the top four teams will vastly reduce the temptation to expand the bracket to include more deserving teams.