To me, the answer is so simple - I'm probably missing something.Portal cant open next week since classes start next week. At the end of the day, 99%+ of CFB players are still students, not NFL players is waiting.
But I agree, the transfer portal has ruined college sports and it will only get worse with the recent ruling allowing unlimited transfers with immediate eligibility.
Make every football college football player be eligible only if they sign a contract. That contract would set up payments, buyouts if they transfer, insurance, penalties for 'opting out' of bowl games or meaningless games if healthy, etc. It would probably mean direct payments from the school to the players, but we have that now, essentially. And there would be salary caps, just like in the NFL.
College football and basketball are now professional, so treat them as professionals. Keep scholarships - that is like a UBI for every player.
The pretense of amateur sports is already destroyed - play in the real world with real world rules.