I know my opinion won't match the "dream playoff scenario" that many people here are proposing...but heck, I don't like the playoff at all (I didn't like the BCS either). So what if you have a co-champion once in a while? Who does it hurt?
Anyway, a four team playoff didn't work. TCU and Baylor got left out and should not have. I know Baylor didn't end up looking good in their bowl, but they beat TCU heads up and had an equal record (although against inferior opponents I guess).
My point on this topic (and I know EVERYBODY is going to disagree) is that if there is going to be a silly playoff, then it should be 8 teams. However, I don't think there should be any "at large" teams selected. I think if the NCAA thinks there has to be a playoff and if people are going to call this a "true" championship, then some changes need to take place.
1) Standardize the rules of college football. Get rid of gray-shirting, over-offering of scholarships, force schools to honor their commitments to the kids to whom they offer scholarships (unless the kids does something illegal or becomes ineligible in some way), and come up with some way to enforce academic eligibility (mandatory NCAA academic audits? Idk how exactly that would work, but something should be done).
2) Nobody gets to the playoffs without wining their conference and that means wining a conference championship game. That would make certain that every team played something of a first round playoff game to advance to the actual playoffs.
* Now I know #2 above creates some issues so here's how we solve those issues.
3) Force every conference to have a conference championship game. I realize this would call for some realignment. If the Big XII(10) wants a CCG, they will have to add teams. Also, if any of the non-Power 5 want to be considered, they too would have to have a CCG.
4) For the love of God, don't make special dispensation for Notre Dame. If they want to be considered for a playoff spot, force them to join a conference (and that goes for any of the other independents for that matter although I don't think Army or Navy would play along).
5) the playoff committee would now have a much easier job on one hand, and a much more difficult on the other. The winners of the Pac-12, B1G, Big XII(10), ACC and SEC would get into the playoff (provided the Big XII(10) actually expands to become a real Big "Twelve"). For the other three spots, the playoff committee decides ahead of time (meaning at the end of the season, but before the CCG) which of the other non-power 5 conferences are the best and those champions would make it in as bottom seeds in the playoff.
So there you go. With my system we wouldn't have to worry about TCU getting left out, and we wouldn't have to worry about an average Notre Dame getting slotted ahead of some team that played in a tough conference, AND best of all, we wouldn't have to worry about the playoff being one Pac 12, one B1G, one Big XII, one ACC and four SEC teams. If you're in the SEC and you want to make the playoffs....win the conference.