I don't think anyone questions his talent, fit on this team, or his worth in today's league.
The only real question with giving up legit assets for him is whether he would resign here. If you don't believe it's likely, you can't trade for him.
Great player, would be great between IT and Horford. If he's committed to taking down the top 2 instead of chasing Tinseltown, Ainge would pull the trigger.