It looks like the celtics would have to ship out 2 or 3 of the following in addition to the #1 pick (Bradley, Crowder, Smart, Brown, Rozier) and would have to give up their rights for Olynyk and Jordan Mickey.
So I think your roster would look more like this:
PG) Isaiah Thomas
SG) Jimmy Butler
SF) Gordon Hayward
PF) Al Horford
C) Robin Lopez
Marcus Smart
Avery Bradley
Tyler Zeller