it can be done but it will generate ZERO profit.
set all these unwanted players at a price tag that match their outstanding current salary plus alpha..
Example : Onana still have 3 yrs of his contract to go at abt 6.2M per year which is about 18.6M ... so the club can accept a transfer price of 20M and used it to buy out Onana's remaining contract.
The way the transfer market works is that even if the club agrees on a transfer price... but the play can still have the final say if he is not happy with the personal term which is typically a higher salary compares to what he is currently getting now. So the only way to force a player out is to pay him off.. same treatment when releasing a mgr who is still under contract.
So by doing that we will be selling with no money to replace them.
And mgr have to resort to using U21s as subs.
The main players will get fatigue and injured eventually.
And player still has final say like you mention. Nobody will want a lower salary in their next club as it will affect their next salary after that even after we pay them off now.
They would rather hope that somehow they will start performing and is able to ask for a higher wage in their next contract with their next club as that club DOESN'T have to pay a transfer fee when the player runs his contract out at UTD.