They should have a Premier Leauge of 24 schools and a Secondary Leaugue of 24 more schools & the rest try to compete to get into the Secondary league.
Every year you have a scoring system based on the last 3 years where the 3 with the most losses points (not counting playoffs) the previous 4 years get kicked out and the Secondary champion & 2 other highest wins points get put into the Premier League.
For the Secondary League you could have the rotation be 4 instead of 3. That way this Secondary Leaugue would have an annual turnover of 7 - 3 up to Premier, 4 down to 1A, and 7 incoming (3 from Premier, 4 from 1A)
The division 1A should have 4 bowl games where the top 8 of wins for the previous 4 years in 1A get to play & the winners go to the Secondary Leaugue the next season.
I like the play-in system, but it should be based and not just wins, but revenue.
Schools with the most wins and most revenue stay in the premier league, but if there is a decline in revenue and wins, they are moved to a secondary league.