It would be sad to see Crowder go, but it would be devastating to see Crowder's contract go. He's not 'untouchable', but all other avenues should be explored before trading Crowder.
And, what? Bradley, Crowder, and the '17 BKN pick for Butler?? That would be one of the biggest heists ever by Chicago. No way in heck Ainge even considers such a deal - especially before the offseason where he has money to spend while keeping all three players/assets.