If you were Danny Ainge, what would you give up to get him, knowing that he's going to be a FA at the end of the season?
They have Marcus Smart whom would fit well next to Harden. Sullinger would be a logical piece too.
Then youngsters RJ.Hunter/ T.Rozier/ J.Mickey/ J.Young
...and draft picks (mavs' 1st, plus 2nd rounders from the sixers/ mavs/ heat/ cavs if I remember rightly).