I'm a big fan of the relegation practice, certainly for the NFL and MLB. I don't see how it would work at the college level.
Imagine having twelve of the best programs:
Alabama
Clemson
Georgia
Ohio State
Michigan
Notre Dame
Oklahoma
Texas
LSU
Texas A&M
USC
Oregon
And they all play each other, with the bottom three teams falling out, and then the three teams from the lower division moving up the next season. You could have maybe 6 or 7 such divisions. Actually the most interesting games would involve the teams trying to avoid the drop.
https://www.sbnation.com/a/college-football-preview-2016/ncaa-football-relegation
Of course some of the teams have moved around, but the principle still applies.