Every player must go into the portal every year. And then we have an auction for their services. If the richest schools want to buy up the best players before the poorer schools get any then they can do that. OTOH, if 20 QBs, say, have been taken by 20 schools and the 21st QB comes up and those top 20 schools try to double down and get depth, the 21st QB might think "They'll give me more money but OTOH I'll be more likely to get to play at one of the poorer schools, so I'll go to one of those and make less money now but be more likely to make the NFL someday."
Voila. The richest schools still get the best teams but we still keep all of college football thriving instead of having it narrowed to 20 elites schools, which would get old fast.
Oh, and if a kid wants to stay at the school he's already at then fine, but he has to pay his way through school.
There you go. Now you can start telling me how brilliant I am.