I've said this on other Noc threads (there have been many), but I can't see Ainge doing it. He is two years younger than Posey, but he actually makes more over the next three years than Posey does. He wasn't willing to give Posey that money, and we know how well he fits here. Why would he give more to a similar player who may not fit as well?
This is not to say I dislike the idea - I love the thought of getting Nocioni for Scal (hopefully with a buyout of him by Sacto so he can come back on a minimum contract) or Baby in a sign and trade, plus Tony Allen, Giddens or Walker, and Pruitt. I just don't have any reason to think Ainge would make the move.