I want to justify this trade but it looks pretty suspect right now. First I hate going for the two nickels for a dime approach; this team has to many assets right now and the roster is going to be really crunched in the next few years--depending on free agency it is going to be a stretch to find Zizic and Guerschon minutes next season. We don't need more guys; the issue for the Celtics has never been finding capable players it has been finding stars, and trading away from taking the slam-dunk number one choice seems like an ass backwards way to do it.
Conversely, I really don't think a star player worthy of trading the #3 pick plus future picks plus current players is out there. Butler isn't worth it, George isn't worth it, hell, with his injuries I'm not sure Brow is worth it. The guys who I would trade all that for is basically Durant, Westbrook, Harden, James, KAT, Giannis. Something tells me those guys aren't available.
Since this trade makes no sense to me, I'll throw out a scenario that doesn't make a ton of sense. Suppose LeBron and Danny have already talked and LeBron is going to opt out and sign with Boston. Celtics then acquire assets to trade for George or Butler. No idea if they would make the salaries work but a five of IT/Bradley/Butler/James/Horford could possibly take down GS. Since any other scenario outside this one makes me want to rip my hair out, I'm focusing on this loony one.