I don't think Unai would ever want him here as JG would want to be the main man at Villa. There is only room for one main man, and that is now UE.
Also, due to his life style, I believe he will deteriorate rapidly once he is past 30. He would want high wages and a long contract, so he would just end up being an expensive Micah Richards. We might get one good season out of him, but then just be stuck with a dud.
I'd steer well clear of him.