I mentioned the Lakers because I think it's the type of franchise Ben would consider going to. It's true the Lakers don't have the cap space this summer, so it would have to be a sign-and-trade.
If Ben makes it clear he wants to sign somewhere else, then the Pistons may want to do a sign-and-trade to accomodate Ben Wallace. And, if Ben likes the Lakers, then it would be in the Pistons interest to sign-and-trade him there as opposed to the chance of Ben playing for Chicago, a divisional foe.
Just a thought.
In a sign-and-trade deal, the player absolutely decides the team, because it's all predicated on that player actually "SIGNING" in order to be traded. Ben could definitely dictate where he goes in a sign-and-trade scenerio.