Obviously KG at Center.
I expect when Bass/Sully are in at Center, they may take the other teams "banger". Sully has great reach for a 6'8" guy, so I expect he can play center. (Similar to Elton Brand playing center despite being 6'8", but Brand was more athletic and had an extra 4 inches in standing reach, so Brand was obviously better suited.) Those options give them some real leeway in what they need from the C spot.
Ideally you count on nothing from Melo - so he's your fourth center and you send him to NBADL.
I think they need one guy to be a KG backup - Steisma, Williams, Hollins fill that role. They are your normal rotation backup center, but will only see 10MPG. You also need a banger backup - that's someone who fills the Perk role, but is not used so much. There may be games he plays 15 MPG, but there will also be games he doesn't dress. If they can get Wilcox back for the minimum or similar, then I think he's a great fit and actually sees an expanded role (assuming healthy.) He's probably the best option, since he already knows the team and can play with KG at PF or C with the other PFs.
So ideally (not saying likely) I'd like to see something like:
KG / Wilcox / Steisma / Melo
Bass / Sullinger / JJJ
Pierce / Green / (Pietrus or Joseph)
Lee / AB
Rondo / Terry / Dooling
Rotation: KG, Bass, Pierce, Lee, Rondo with Green, Terry, AB (start him once healthy and if he gets to where he was this year) getting primary minutes off the bench & Steisma, Wilcox, Sullinger splitting minutes like Brown, Powe, BBD in 2008 (meaning two of the three get minutes on a per game basis, but utilization averaging out over the season.)
I think Williams and Moore are still on the team because it gives us throwaway money in trades. Even if Dooling is S&T to acquire Lee, I expect he could be cut and resigned. (Dooling for $2.5, Moore, Williams + $3m for Terry or Lee, receiving team could cut all three guys and make $0.5m in the trade, plus get an extra late second rounder.)