Great debate with folks who know the game. I can't do individual player analysis to this level, but, I can throw in my understanding of "deals" which is what might happen.
Bulls don't have a gun to their head. This diminishes the possibility if "Danny I have a gun right here" Ainge getting the dynamic he needs to get Butler.
Why would Ainge have a strong interest in Butler? My guess is, at this time, Ainge perceives the Celtics as a solid offensive team. They score a ton, their PG is an offensive monster and Smart is a defensive monster. The two guards combine well don't they? The lack of AB has thrown the spotlight on Smart/IT and things are rolling. I suggest, Butler's offensive/defensive balance maybe attractive to Ainge. Not sure why else Danny would be willing to trade for Jimmy.
Now, Danny's history...he wants to turn that BKN draft pick into a player that has potential for dominance. A young college player like Fultz has "potential" Butler has specific measurables.
Like any GM, Ainge has blown his share of draft picks hasn't he? He might trade that number one pick and one of his starters for a player "like" Butler without hesitation because he knows that Fultz/whomever needs three years, and a lot can happen in 36 months. Butler on the other hand, will need about three minutes.
Also appreciate the posts that point out that NBA rules simplify it for teams to keep their star players...Boogie, Hayward...etc. With this understood, Melo, Butler possibilities get a very hard look as, they are RARE...really rare and thus, getting a "playoff calibre" starter in return for a 19 year old "potential" NBA starter (draft pick) is a very big deal.
Personally, I'd prefer the addition of a "big" with the understanding that there is no "dominance" to be found in available bigs at the moment.
(Thanks to everyone at the forum for patience. I have no regular internet making replies out of date. Really enjoy the battles here over the years, the passion is unmatched. I have read the Fakers are "trying to be like the Celtics." How's that workin' out LA?)