How it wouldn't work
Any form of four-team system: plus-one, whatever. First, that's not a playoff. That's old boys disappearing into the back room and declaring a champion. Second, really? Interest in the non-champion BCS bowls has been steadily dropping because people realize what they are now: consolation prizes. Besides, there are six BCS conferences. Tell me how that's going to work. Uh-huh, that's what I thought.
An eight-team playoff. Case in point: 2009. Six BCS conference champions – that's a given, as mentioned above. So that leaves two spots, and which team are you going to exclude?
a) Unbeaten TCU;
b) Unbeaten Boise State;
c) One-loss Florida. (Bonus: they're the only one-loss team in I-A football. Look it up.)
Exactly. Two at-large berths aren't nearly enough. Yes, I know, not every season will see five unbeaten teams heading into the bowls, but every season's going to have a number of qualified candidates from outside the power six, and remember, the old BCS was expanded under threat of legal action. They can't very well shrink the field back down now.
How it would work
Sixteen teams. First-round games at campus sites, quarterfinals at three permanent sites, say Tampa, Jacksonville, and San Antonio, with the fourth spot to one of the existing BCS bowls in rotation, then semis and final at the other three bowls in rotation.
I picked Tampa (Outback), Jacksonville (Gator), and San Antonio (Alamo) for a combination of longevity and geography. Ideally, you'd have a western site, a southwest site, a southern site, and a southeast site, but I don't know that there are enough bowls for that.
Anyway, the teams: 11 conference champions and 5 at-large teams. Oh yes, all 11. It's an NCAA championship, so that's how it works, and anyway if you think you're excluding any of the other conferences, you would be wrong.
What it would look like
Version 1: how the computers might see it
(16) Troy at (1) Alabama
(15) East Carolina at (2) Florida*
(14) Central Michigan at (3) Texas
(13) Penn State* at (4) TCU
(12) USC* at (5) Cincinnati
(11) Pittsburgh* at (6) Oregon
(10) Georgia Tech at (7) Boise State
(9) Ohio State at (8) Virginia Tech*
At-large teams marked like so*. Assumptions: no more than one at-large bid from a conference, and teams from the same conference may not meet in the first round. To avoid this, teams may be moved a spot from their original seeds. (In fact, at first I had a Pitt-UC rematch, a USC-Oregon rematch, and a GT-VT rematch originally.)
Troy-Alabama? Coincidence, plus the Sun Belt sucks. Florida as #2? That's how the computers see it, and we're thinking an RPI-style system, not the crap that currently puts human guesses above carefully-research systems.
I just don't think you can justify three teams from one conference when there are five at-large bids for everyone. With a 24-team playoff like I-AA has, I think you could allow four; with a limit of three, you might drop pretty far down to pick up other teams. LSU is 10th in both Sagarin and Massey and Arkansas averages 14th. Miami is 11th in both and Clemson averages 19th. If you draw the line at 4, that shuts out Mississippi ... but I think you kind of have to, no one wants to see a second-division power-conference team in the playoff. (Hear that, NCAA men's selection committee?)
Version 2: how the BCS might see it
?? at (1) Alabama
?? at (2) Texas
?? at (3) Cincinnati
(13) West Virginia* at (4) TCU
(12) BYU* at (5) Florida*
(11) Virginia Tech* at (6) Boise State
(10) Iowa* at (7) Oregon
(9) Georgia Tech at (8) Ohio State
Same notes for at-large teams, multi-bid conferences, and first-round meetings. So the first problem is that the BCS stops listing teams at 25, so we have no idea where Central Michigan, East Carolina, and Troy would fall. (A cynic would list them in order by wins because he'd say the BCS would understand anything more.)
No teams needed to be shifted. Iowa gets the Big Ten's second spot instead of Penn State (margin of victory being important in a real ranking system, but in the neutered version, PSU gets virtually nothing for whipping bad northeastern teams). West Virginia sneaks in ahead of Pitt (which has to hurt considering the Big East "championship" – makes you wonder if people even watched that game, but I think we all know the voters don't actually watch games).
BYU slips in ahead of USC, and to be honest I'm fine with that. In fact, in an RPI system, I doubt USC would get in, because they were tied for what, fifth in the Pac-10? They finished their season terribly. Maybe the conference was tough as a whole, but cry me a river. If you're taking a team from the Pac-10, it's Oregon State, right?
Of course in an actual BCS-based playoff, BYU wouldn't have a chance in hell (pardon the phrase), because they're not in a BCS conference, and the power conferences would always get the at-large bids.
Anyway, you see where this is going. TCU-Boise State is a nice matchup, as is Alabama-Texas and Florida-Cincinnati, but that will still leave at least two unbeaten teams, and if you think that doesn't matter, well, you were probably happy with the poll-determined champions.
The BCS is a limited system put in place by greedy fools who had no clue and updated by fools who still have no clue. It will be replaced by greedy people who have a clue. (Make no mistake, a playoff will be introduced for money, not because it's a fair way to determine a champion or because every single sport at every level of NCAA competition has a tournament except I-A football.)
Looking forward to that Troy-Alabama matchup? Too bad. Waiting to see if Cincinnati could make it to the semis or if the TCU-Alabama winner would trip them up? Keep waiting.
In the meantime, we'll have the Orange Bowl. Iowa-Georgia Tech. Mmm-kay.