Bring both off the bench.
Rondo/Terry/Christmas
Lee/Bradley/Dooling
Pierce/Green/Joseph
Sully/Bass
KG/Wilcox/Melo
I'd play Sully with the starters because playing him between Pierce and KG would be best for him, his game, and his growth, while allowing Bass to shine at his best role clearing room for Green and Terry to slash off the bench.
That's an interesting look with Lee starting over Bradley. It could make sense, at least during the grind of the regular season.
With Pierce and KG in the starting lineup, it pretty much dictates that the starting lineup will be slow tempo. Sullinger is very much in that half-court, slow tempo mode of player.
Having Rondo and Bradley playing with a slow tempo frontcourt might be an inefficient use of their athleticism.
Bradley is probably the best defensive PG on the team, and I still think scoring PG is Bradley's ideal position long-term.
Bradley/Terry/Green/Bass and Wilcox or Melo is certainly an athletic change-of-pace look.
I think come playoffs Rondo and Bradley will be the starters, but for getting through the grind of the regular season, staggering Rondo and Bradley's minutes might make sense.
I'd only quibble that Sullinger would end up playing the center role while KG plays 4 in that starting lineup.
Bradley starting out injured pretty much seals the "who starts at the 2" call for me, and then once Lee has it through training camp and the first couple of months of the season, it *should* be his spot to lose. Terry is naturally coming off the bench, and Dooling should naturally never actually play.
But if Sully starts, spreading the floor with Lee over Bradley makes some sense, too.
A tight playoff 3-guard rotation is going to be quite the competition, though. Lee v. Bradley, if all are healhty, with Rondo and Terry as locks. I'd bet on Lee, but really like Bradley.
The forwards feature the same problem, with Pierce, Green, and Bass as locks for minutes. The other minutes in the 4-forward rotation will depend on Sully's development, but both Wilcox and KG can play there (but are better/quicker at the 5 and should split time there), or an even 3-way split is possible. I'd prefer to work Sully in fairly quickly, but there are as many points of view on that as stars.
KG and Wilcox split time at C, and we have a 9-player rotation.
But if you like Bradley too much to go with only 3 guards, we have a Hubie Brown-esque two-string team. This is one heck of a roster...going to be hard to keep everyone happy.