If Danny signs Pietrus he's put up a great offseason (A+ if Pietrus signs for the vet min). When you have no cap space, you can't go after a lot of players, and the Celtics did very well.
I wouldn't mind Blatche for vet min, he gets Sean Williams spot and Melo will take Stiemsma's. When you have Wilcox/Sullinger/JJJ to back up KG and Bass, you can take some chance on a low risk/high reward gamble. But you can't trust him as Plan A.
I think this roster would be great:
Rondo/Terry/Moore
Bradley*/Pietrus
Pierce/Green/Joseph
Bass/Sullinger/JJJ
KG/Wilcox/Blatche/Melo
looks thin at PG/SG, but Terry and Moore can play mostly the 2 and some backup 1. I'm not sold on Moore yet, but by playing him in Bradley's absence you could reap some benefits in the form of a rotation player/trade value.
If Blatche doesn't buy into the team, cut him when Melo is ready to play some minutes. I know he's a PF and not a C, but as a 3rd string big man he has the size to play both positions.