I actually think that title IX would be a significant handicap to any breakaway, even if it was just for football. Title IX is federal law, not some NCAA regulation, and if you don't give women the same opportunities it has some serious implications. So you need to set up not just a football structure, but one that covers the myriad of womens sports that schools rely on for compliance. And the NCAA, if they have any guts and any b@lls will draw a line in the sand and say its all or nothing. It is one thing to run a 4 or even 16 team football tournament. Do the Power 5 conferences really want to run a womens basketball tourney? Or Soccer? or bowling? It suddenly doesn't look so cool. As for incorporating football as a semi-pro/minor league entity, I suspect it won't take too long before it really becomes a minor league entity,with all the problems associated therewith. How long before the NFLPA decides to organize the players? Or some Heisman trophy candidate decides to jump from Texas to Oklahoma or hold out for a better contract? And when it has to compete with the NFL it will be just some minor league.
Finally, there is going to need to be some form of regulatory entity.. there just is. And this is different from the NFL. LSU will have different values from North Carolina, Michigan from Florida. And that will be a huge issue in setting up any new structure.