I wouldn't even do that. If he is still here after the transfer window is shut but refusing to sign then the he should be told to stay away from the club altogether. Pay him to stay at home and rot and not even play for the U23's, it'll cost him a whole year with zero game time at any level and could effectively ruin him. This is a last resort obviously as if the window did shut with him still here then surely even Ross wouldn't be stupid enough to refuse a new deal at that stage.
Pay a talented footballer to stay at home? Are you for real? If we're paying him regardless we may aswell pay him to play than to stay at home.