Thinking it over, I'm pretty sure he's not superstar-guy anymore, but he's still a weapon off the bench. I think his shooting (excellent range) will complement Nate well, with Nate being the playmaker and McGrady coming off screens or posting up instead of running 90's style isolations.
I can also see Quisy doing well sharing 3rd option duties, but using his length at SG instead of SF, but taking the main defensive assignment anyway, and hitting baseline jumpers or making the extra pass. I think Quisy would do fine.
I would want another big guy, perhaps a running big (likely a PF, with BBD at C). Nate/Quisy/T-Mac/Someone/BBD could be an effective 15 minute unit, likely expanding the lead against most teams, while showing a different look, requiring the other team to make an adjustment.