I agree that McAvoy makes dealing him easier, but we saw last year how much that depth meant when half their defense went down. Sure, it's unlikely to lose that many guys that quickly, but even losing one or two guys is enough to throw them off. Lauzon and Zboril are still a few years away, and it's unclear how close O'Gara and Gryzlyck are from contributing in the top 6. As is, that would leave them with Chara-McAvoy, Krug-Miller, Postma?-McQuaid pairings, and little depth otherwise. It's not horrible, but it's not good.
Cap wise could it work? They would have to keep McQuaid for their defense, and Belesky is unlikely to be moved back to them without partnering some high picks with the contract.
I don't see it happening, but what do I know?