The thing is, Crowder would already be a nice asset. They could flip him and his cheapo contract to a team that wants to win now and needs wing depth and probably get a mid first rounder.
Bradley is nice but hard to re-sign. Still, you'd get him for a year at least, at cheap money.
The problem is the Celtics have amazing picks (BKN/LAL or SAC) or bad ones (BOS 18/All the heavily protected ones). They don't really have good/mid-level ones (say, 8-15 range).
I don't know what other teams are offering, but I would offer Crowder/Bradley/BOS18 and maybe a 2nd round pick or player (Nader?) if needs be. I mean, what is LAL offering? Randle? Crappy future picks as well? They can't even offer their 2018 pick because we own it. The earliest first round pick they could offer is 2020.