First off the B1G and the SEC break their football programs away from the NCAA. The B1G and SEC poach a few more teams like Notre Dame, Clemson, Notre Dame, bumping the B1G football conference to around 24 and the SEC to 21.
The B1G and SEC organizes into 3 or 4 divisions for football. After the season the B1G and the SEC will have conference tournaments with the 3 or 4 division champions and an at large teams if there are 3 divisions. That will happen at higher seed's home stadium and the title game at a neutral stadium during the first 2 weeks of December. 3rd week all the teams except those involved in the conference title games will play in a B1G SEC challenge type bowl week, (3rd B1G vs 3rd SEC), any extra teams can play some Big 12 scrub. Jan 1 is the college superbowl between the B1G and SEC champions.
Transfer portal would open after the 3rd weekend in December when all but 2 team's season is finished. 12 game regular season, no FCS teams allowed, as many conference games as the individual conference wants. Rankings don't matter as playoff spots are tied to division standings not polls, computers or committee.
Another portal window after Spring football. Spring football can finish with a scrimmage against another team.
Recruits can commit anytime once their Senior year starts. All players are required to sign a contract and join the B1G/SEC player's union in order to get paid. The contract will help limit transfers but also give the players robust health/career insurance. Players can sign their contract for any length that they and the coaches agree to, from 6 months to 5 years. Players are free to transfer if they are not currently under contract, players can not be cut if they are under contract and take up a roster spot. Players can transfer early but it incurs a one season ineligible penalty. NIL is allowed but has to go through a clearinghouse to ensure fair market value for the NIL, no more pay for play, monitored by somebody that has some real punishment authority, similar to how the NFL doesn't allow maneuvering around the salary cap.
Both the B1G and the SEC agree on a maximum amount to spend on football "revenue sharing", which will effectively act like a salary cap. The B1G/SEC also agree to a roster limit, maybe 120 or so. 5 year clock with 4 years of eligibility, no more 4 game RS years. Only exception is post season games won't cancel a RS season, current medical hardship rules for a RS year, but no more 6 year players.
No limits on staffs, travel rosters etc. Players can have agents. Players can go to the draft and come back, as long as they haven't used up their 4 seasons in 5 years clock and have remained academic eligible. Don't like where you were drafted then play another year in college.