First off, this will never happen. I'm aware football runs the world of sports, but it'd be too easy for those schools to tell the top 20-30 to buzz off. Hey you want that league cool, then you don't get KU Duke UNC for bball or Vandy Oregon st for baseball etc. It's so much bigger they just can't do it. Furthermore, good luck with rivalries, it won't be as fun for Michigan when they don't get MSU on the schedule and half their games are across the country.
I've said this general idea before but I think it's so easy for football. You take all the D1 (FBS/FCS) teams, currently at 136 and divide them up into 3 divisions. Each division plays against only teams within their division and then you have relegation/promotion. I'd go something like 44-44-48 teams with 6 teams per division going up or down each year. Then have say 4 "conferences" at each level. Split them up as best you can geographically to maintain rivalries. Will be small changes year to year based on who is in. You play the other 10 teams in your conference Each year plus 1 from the other 3. 13 games a year regular season. 12 team playoff in each. Rd 1 playoffs at home, remaining 7 plsyoff games at bowl spots. Lowest division hey your at the sun bowl or wuick lane, middle hey you get the gator bowl, top big 7.
Semifinalists plus top 2 in the rankings after that promoted, 6 lowest ranked out. Literally every game matters, teams that do well move up, you don't move down. The TV deals would all fall under the NCAA or whatever group you want to call it. So the top division teams get paid more. Gives every game meaning, keep most rivalries, groups teams better, plenty of storylines. MN NW this weekend Literally means nothing, we win we play in a bad bowl, we lose we play in a bad bowl. Imagine now this game decides relegation. Now that matters. Sign me up!