Straight swap for Tuohy would be fair. Tuohy would dominate at the SCG. Both clubs address a need (Mills goes to the midfield). I don't want Tuohy to be kicked out though. Only if he wants to leave.
I worry about Mitchell's price which will be astronomical and attitude. He is a GOOD midfielder but he's a distant fifth to Parker, Hanneberry, Jack and Kennedy. You wouldn't break the back for him.