I love relegation in English soccer, I really do. But the business model for major college football is dramatically different than the business model for English soccer.
English soccer is a professional sport, and it is focused on only one sport, one team. All revenue from operations, goes back to that one sport, that one team.
College football is not actually one sport. Each university athletic department supports multiple sports, which are all funded by football revenue. Dynamic/non-stable revenue distribution is something a university athletic department just can't tolerate. It completely breaks the model. They need long-term stable, predictable, assured annual revenue input, in order to manage all of the other sports.