Priority 1: C's need a big that can bang and play D. Maybe OKC will amnesty Perk? He'd be good Center behind KG. (Saying that only in jest... kind of.)
Priority 2: C's need a wing that can start at SG until AB comes back, and then provide a third option at both the SG/SF going forward.
Priority 3: C's need to make a decision about Moore as the "third string" PG (behind Rondo and JET), if they cannot count on him they need to resign Dooling or maybe Daniels for insurance.
If all three done, the team will be:
KG / new center / Melo
Bass / Wilcox / Sullinger / JJJ
Pierce / Green / Joseph
AB / new wing
Rondo / JET / Moore (or Dooling)
With JJJ as fourth PF, it leaves us a little thin at SG, but because the PG depth and SF depth can cover that spot, it's not a big deal. (e.g. JET will play a lot of minutes with Rondo IMO.) This is even more true if you consider JJJ a combo forward and also depth at SF.
I don't expect Melo, JJJ, Joseph, or Moore to play a significant role. I think Sullinger, the new center, and the new wing play platoon role based on the other team. Which means the top 8 guys in the rotation are already signed.