if you do a playoff, the final 8 should be your 6 major conference champs, plus the highest ranked of the 5 mid-major champs, and one at-large team. (yep, just one).
the message...win your fuckin' conference or quit your bitchin'. this limits so much of the beauty pageant aspect of things.
this season, barring a conf championship game upset, you would have TCU beating out Boise for the mid-major spot, plus the Florida/Bama loser getting the at-large.
I would work them right into the existing 4 BCS bowls, and even maintain (and enhance) the traditional bowl tie-ins.
you put Big 10 and Pac 10 into the Rose Bowl every year as a quarterfinal. Some years, when OSU and USC are both top 4, it would seem unfairly tough; other years, like this one, it might seem too easy, but I think it balances out.
you put the SEC champ in the Sugar Bowl every year, ACC champ in the Orange Bowl, Big 12 champ in the Fiesta. Big East, mid-major and at-large are the floaters. use the BCS rankings to sort the teams 1-3 in each group and flip them (so the highest ranked amongst the second group plays the weakest of the 3 traditional tie-ins).
so, to illustrate with an example, let's say the favorites win out and the BCS standings hold. I'll pick Florida to beat Bama, and we'll assume that Bama drops below Texas, but ahead of TCU and UC.
first, the easy one, put tOSU (9) vs. Oregon (10) in the Rose Bowl.
then, take Florida (1) in the Sugar; Texas (2) in the Fiesta; and GT (7) in the Orange. the other three teams would be at-large Alabama (3), mid-major TCU (4), and Big East champ UC (5)
so, UC would play Florida, TCU and Texas, and Bama vs. GT.
take your four winners and put them in the semifinals (seeded by the final BCS rankings)
the four BCS bowls have already committed to a second game at one site every fourth year for the championship game, so you just slide that back a week. the only question now is the location for the two semifinal games. you've got three choices: 1) rotate the remaining BCS sites, 2) open it up for bids like the basketball tourney, or 3) my favorite: home games for the higher seeds. you don't have to worry as much about fans travelling to three straight games, plus you reward those top two teams that would now only have to play one game for the title.