For that kind of money, I say: do it. And I'm not really a big fan, but for the bench he's top quality. He had a great season with AVB and played like a beast in Copa America. The rest of his career, including is actual moment (before the injury), has been average.
Still, I'd prefer Montolivo who could cover for Pirlo as well.
Guarin is a Vidal type player, no?
I don't know if he could work instead of Pirlo.
More or less, yes. But he's a bit more offensive approached, like Marchisio.
No way.