I see a problem with the portal system in that money buys results, and teams that do a lot of coaching, and improve their players get nothing in return. I think that this can be fixed with a new rule that required any team that takes a player from the portal to compensate the team from which the player came.
Thus, if Ohio takes a freshman, and coaches him up, but then loses him to the portal, they would get some compensation. On the other hand, if Ohio were to take a Division 2 or FCS player from the portal, they would have to give up compensation.
That would reward the teams that are actually doing the best job of coaching up their players, and would help to slightly equalize resources, as money would, in general, flow down to P3 to G6, and down from G6 to FCS. I don't know if their is a legal way to actually do this, but I do think it would improve the overall function of the system, and enhance fan interest.
“We have two ears and one mouth so that we can listen twice as much as we speak.” ― Epictetus