Rondo needs to stay, rehab and start playing after the All Star. The same goes for Sully. These two are Celtics, hopefully for a long time.
Try to get a couple undrafted rookies (CJ Leslie, Kenny Kadji, Myck Kabongo...) Send Shav and DJ White somewhere for a future 2nd rounder, and do the same with Reggie Evans friendly contract. Package Humphries, Bogans and Jordan Crawford with a protected future 2nd rounder to Cleveland for a TPE to use at the right moment. Cleveland will need to be over the cap floor (not sure how much after they sign their picks), and those are expirings they could keep or move later.
Get a veteran PG (Dooling?)and make him compete with TWill. Play Bradley and Lee at the SG slot, and start Green and Bass at the 3 and 4. Start Olynyk and let Melo backup him. Use Gerald Wallace as the main backup at the 3-4. Send Iverson to the Rock Lobsters. Roster could look like this to start the season:
Dooling/TWill/Rondo(injured)
Bradley/Lee/Kabongo
Green/Wallace/Joseph
Bass/Wallace/Kadji/Sully(injured)
Olynyk/Melo/Iverson(DLeague)
This is a bad roster, but filled with young players to showcase. With Dooling as a veteran presence, and some experienced players (Lee, Green, Bass and Bradley), I think Wallace and the young kids will mesh well in the locker room.
The team will suck without Rondo and Sully, but there'll be minutes for the new guys to show what they got. After the All Star weekend, Rondo and Sully get back into game shape and show they're healthy, but the Cs still get a top 10 pick (or higher). If the pick is good enough to bring a building block, great. If not, use the pick plus the TPE and/or young pieces to try to get an All Star.
The Celtics need to suck only for a year. Healthy Rondo/Sully/Green/Bradley and maybe Olynyk/Melo are a nice group to add on.