The proposal includes a caveat saying that the players would not be allowed to follow the coach to his next destination which makes a lot of sense.
If the coach you committed to ends up leaving, why should you be penalized? Instead, allow the student to re-open their recruiting process in effect and let them choose a new coach / program which might fit their abilities better.
That being said, I agree that the net effect of the Big 12 proposal would be that the rich get richer. When an AAC coach gets poached away because they did so well, all of a sudden, all their best players are effectively fair game.