I doubt he will stick around after your claim war, but that shouldn't be too much of an issue. Find out what court he goes to, if it's one in your lands, likely since you are both Italian, then grant him a small city some where, arrest him and banish. If he ends up in some other court, marti-marry him to a female in your court, grant him a city, and banish him.
Easier said then done, sometimes. The AI often doesn't accept mat marriages for political concerns and this would be cause for one. I'm finding trouble with some marriages that my devious plans are 3 generations down the road.
But like you said, he might end up in Italy. Too, I'm interested to see if a greedy empire wants the country. I think historically it did late game but I never saw it transpire in my game -- the horde was up north and the ERE had been pushed back. It would be a hoot if he landed in the HRE with a tyrant Emperor... well from this side of the game.