My conclusion watching the C's in the limited games I have is that Rondo, Green, and Sully are worth building around. Find an elite defensive center and find a more consistent shooter to replace Bradley and you'd probably have a near contender, at least in the Eastern conference.
The rest of the roster, outside of Smart, I am rather indifferent towards. None of them particularly seem like 'keepers'. I could see a few staying on a role players off the bench, but would be fine if any of them were traded for better fitting players.