#16, #23, #31, and #45 this summer; Boston's pick in '17 (which includes pick swap with Brooklyn) and 2 more second rounders in '17; Terry Rozier, RJ Hunter, and Avery Bradley.
Boils down to 3 first rounders, 4 second rounders, 2 prospects, 1 asset. Seems like it might be enough to nab Butler if he's really on the outs with Chicago but I'm not sure if I'm deluding myself. I'd throw in Sully in a sign-and-trade, too.
I'm imagining a summer where the Celtics get lucky in the lottery, draft smart, sign sign Al Horford, and execute a trade like this for Butler. I think that's a championship contender.