promotion system

We have 130 FBS schools. Divide into East and West Region.
If you used Chicago O'Hare as the midway point, that equally divides the P66 (BYU & ND) in half. The G5 schools are also divided in half according to region.
Everyone plays all 12 games in their region/tier

Tier 1:
13 in the West vs.13 East (Champs meet for national championship)
Tier 2:
13 in the West vs.13 East
Tier 3:
13 in the West vs.13 East
Tier 4:
13 in the West vs.13 East
Tier 5:
13 in the West vs.13 East

I'd do relegation and promotion this way.
Champions of lower tiers E and W get automatic promotion. Play one another for National Tier championship. But promotion in a lock for both.

Last place of upper tier gets automatic relegation.

2nd place team plays in lower division plays 12th place team in a promotion/relegation battle
3nd place team plays in lower division plays 11th place team in a promotion/relegation battle

All other teams get one additional game for bowls or to hook up with a rival who may be in another tier or region. For example, if Virginia Tech finished 9th in Tier 1 East and UVa finishes 4th in Tier 2 East, they could meet in C-ville or B-burg. Unless one of USC and Notre Dame were in the title game or in a relegation battle game, they would play at this time.