Wild thought.
Currently, P4 conferences (via their affiliated schools) have morphed into a farm system for the NFL. These universities are merely transitional spaces for semi-pro athletes to develop their skillsets for a shot at the big league (NFL).
Pushing your narrative a little, you're basically suggesting another minor league system.
P4 is football's equivalent to "Triple A" - the minor leagues.
Under your model, non P4 conferences, will just be an extension of "the farm system," akin to "Double A" - again, the minor leagues
I think we are already there. It's just not formalized.
The NCAA wants the masses to think they are pumping out a fair product, but the system is rigged. The more they rely on the benevolence of alumni and die hards to fund NILs, the more investors are going to expect (and demand) an ROI. The likelihood of satisfying the masses with this idiotic model is somewhere between slimmest and none.
People can point to the ratings all they want. The current model does not seem like it is very viable for the long term. Far too many factors are influencing my stance.
In time, NCAA football and basketball will be done. I just don't see how this is going to work out in the long run.