The answer is to flip the season. Right now the P5 plays mostly G5 before the season starts but then don't want to play them at the end of the season. Change it to everyone in Div 1A (or whatever it is called now) plays one team from Div 1AA and one team from another conference as a sort of "preseason" and then conference play starts. Everyone, even the worst team in a league, at least then gets 10 games which is what it used to be back in the day.

The P5 sends the league champion and then one team of their choosing to the "playoff". The G5 sends their league champion and there is one at large spot for whomever giving you 16 teams. Divide the 16 teams into pods of 4, which plays a round robin. The winners of the pods then start a 4 team playoff.

The two teams in the championship game would then have played a total of 16 games, which really is not that much given the current environment. The real selling point of this would be the vast amount of money which this would generate, which would be WAY more than the current amount due to the shear volume of games which have impact on who is crowned the NCAA football champion. Even the greedy P5 would have to see the $$$ here.

By the way, I am not guaranteeing any of my numbers are correct, I just thought of this on the spot.