I would offer our 2016 Celtics pick and Smart for Okafor.
I don't think the 76ers would do it, and nor do I think Okafor would be a good fit on this team. Hes woeful at shooting, free throws, and has been a terrible passer.
But hes infinitely talented; a promising big man with sky rocket potential is far more valuable than a player like Smart, who brings hustle, intensity, and intangibles plus solid defense for a guard.
But I would expect the 76ers would want a lot more. And I think Ainge would refuse to do so.