FB would drive this, but BB would follpw eventually. Money will dictate, political alliances be some factor.
If the P2 format means more big games, then that's what will happen.
If too many teams eith enough cache feel left out they will go in another direction.
A promotion/relegation model would mean huge money, a lot of very meaning full region games and give the big money programs enough of an advantage to allow it to happen. But first, it would require an act of Congress to flush all the disparate conferancd and corporate contractual relationships/NCAA rules to make a fresh start.
A top division of 24 teams with a second division of 24-48 teams would work depending how you sort the second division. I think 24 in two divisions with the top team in each division plus a playoff of the next two in each division getting promoted and the bottom team in each division and the playoff loser of the next two worst teams being relegated.
That takes care of 48 of the 130 or so D1 programs, the rest would be sorted into regional groupings with 3 of those teams moving into the 2nd division via some playoff system. You could add regional sub tiers and the number of teams participating increases.
This is equivalent to the English Football pyramind system. Your Yankee and Ivy Conference equivalents feed into a Big East level league with the winners joining the national 2nd division and the winners of that division promoted to the top national division.
In an alternate version of history. The 2007 UConn teams likely makes the 2nd national and assuming they stay up, the 2010 squad gets promoted to the big time before PP and his successors tumble the program back to the Yankee league by 2015.