I'm agree as a formula to stop the AvQ manipulations, it could be effective and easy to implement.
I just would add, that it can be enough with a 20% as min' AvQ, and that the player don't need to be released from the club directly if doesn't have the 20%, the contract could give us 7 days to train the player till 20% and then allow us to renew the player.
But overall, a good soloution to keep the margins inside adequate parameters.