Florida State or Miami. Those are the 2 schools that make the most sense in my opinion.
He already knows the sunshine state inside and out for recruiting purposes, and the ACC is ripe for the picking. There isn't a competent football program in that entire league outside of Clemson, SC.
If Urban takes his talents to Talahassee or Da U, he instantly makes the Seminoles or Canes the #2 program in that conference. Then he can do what he does best: create a culture obsessed with chasing the top dog (Clemson), and doing everything in his power to knock the Tigers off the ACC mountain top.
If Urban Meyer resurrects one of those 2 struggling but proud football programs in FLA, and he is somehow able to win a Natty at a third school... his legend will be cemented as one of the top 3 coaches of all-time, if not the best.