If the powers that be think it's optimal to compete with the shield, they will meet a deserved and fitting end at that point.
However, your point about eligibility years is a good one. If this becomes separated from academia that will absolutely be a point of contention. I think it would be in the best interest of college football to keep it at 4 (with 5th or 6th years being incorporated for redshirts, injuries, etc.).
PS I still think you can treat them as students, just let them major in football. It's career development in principal, so I don't see much of a difference. This will all get figured out with a super league that includes a CBA with the players.