With the current roster, Terrence Williams would be my first pick. Then, if they can't find a reliable defensive big who can play ahead of Jason "MVP" Collins, Yi would be my second. Yi was a DA favorite back in his draft, and it would be great for the Chinese fans and market.
If the salary cap allows it, I would like to see Barbosa waived and staying around the team for his rehab, just like Green last season. If waived, or if a trade happens, T-Mac could be a useful 12th player for 10-12 minutes or less.