The salary cap in the NFL is part of the CBA which is negotiated. The NCAA doesn't negotiate. They just set the compensation at a relatively low, fixed rate.
I'm not sure how this will all work out over the next few years, but I really think the only possible solution is a CBA for all student athletes. You can address Title9, non-rev sports inequities, tv money, NIL, etc etc. And it will all be legal. NCAA will be just like any other sports league - which it is anyway.
Alternately, P5 CFB and MBB will split off from the NCAA, become their own leagues with their own CBAs, and the other non-revs will remain bascially as they are within a hollowed out NCAA.