I have given this problem a lot of thought over the years, being a huge college football fan. And, while your ideas have merits, you have two major opponents in this instance: the conferences and the individual universities.
There is an embarassing amount of money involved in college football, and the major conferences/schools aren't ever going to be willing to subscribe to a system that would "demote" them at any time for a poor season. There's a huge disparity between the payouts of BCS bowls and those of lesser bowls, and major schools aren't going to give that up in favor of promotion/relegation. The colleges, conferences and fans wouldn't accept that sort of change.
Division 1-A college football is the only NCAA-recognized sport that doesn't have a legitimate playoff system. The old bowl system is dying slowly, and fans/commentators (even some college coaches, athletic directors and presidents) are clamoring for a playoff system.
The idea is that all of the BCS conferences (ACC, Big East, Big Ten, Big XII, SEC, Pac-10) would all have automatic berths for their champions, and either two, four, six or eight at-large berths for the remaining highest-ranked teams, and that they would play in "bowl games" that rotate through (so that each bowl in the rotation has the opportunity to host the championship).
The big problem with this is that it could seriously affect attendance at bowl games that aren't hosting the championship, as some fans would choose to wait to attend a more-important game as their team advances through the playoff tree. And, a team's fans (specifically, how well they "travel") are currently one of the (unofficial) selection criteria. A team that gets a lot of its fans to attend a bowl (i.e, a team that "travels well") would sometimes get picked over a team that doesn't.
Now, I personally think that theory is bunk, but the people who make all the money from the bowls are the hardest ones to convince.
Still, I hope that college football will see the light and set up a legitimate playoff. Heck, eight teams would be enough for me, still allowing another 20+ bowls to be played for the teams that don't make the playoffs. I'm not looking for something akin to the NCAA basketball championships, just looking to have the debate shift from the snubbing of the 3rd-best team to the snubbing of the 9th-best or 17th-best team. That's more palatable, and it also means more good football between college powerhouses. 
Oh, yeah. Go Huskers!
Davy Jones
"Frightened? My dear, you are looking at a man who has laughed in the face of death, sneered at doom, and chuckled at catastrophe! I was petrified."
-- The Wizard of Oz