Outside of games against ORL and LAL (and maybe a few others with quick offensive centers) I like Shaq starting.
First Unit / Second Unit is hopefully nonsense. I don't think this team can or should play ten men. One of the bigs Shaq/Perk/JO/Baby is going to get the short stick if they are all healthy and get only reserve minutes. If JO was healthy all year, I'd guess it's Perk. But now I think the window has opened that JO will be the 5th big man. (I'm assuming no trade - if they could count on the health of the centers, then I'd try and trade one of them, but I don't think they can.)
We're probably looking at a rotation in important games where Pierce or Allen is on the floor all the time and Rondo is playing 40 minutes a game. I'm discounting West's ability to break into the rotation for now and assuming Nate will stay on, then we are going to see something like:
Shaq / Perk
KG / BBD
Pierce / Daniels
Allen / Nate
Rondo / Nate
What should dictate who starts is how it sets up the remaining rotations - either way I think the starting group will be very good.
For the bigs (assuming Shaq starts) I'm guess Shaq is the first sub out then Perk comes in. Perk stays in when BBD comes in for KG, then BBD stays in when KG comes back. Then BBD goes out and either Shaq or Perk would come back based on game situation. Start that over for the second half.
For the wings and guards it's a bit more freestyle, but you'll see something like:
Allen out / Nate or Daniels in
Rondo out / Nate or Daniels in
Pierce out / Allen in
Nate or Daniels out / Rondo in
Nate or Daniels out / Pierce in
When Rondo is out, we're more likely to see iso offense from Pierce or Nate as the primary offensive weapon, with the shooters as a second option and Daniels as a third option. I actually think this favors having Perkins in when Nate is in for Rondo, there will be less passes to the post and Perk is worse at those. There will likely be more jump shots, and I think Perk is a better rebounder. I also think the wing / guard defense drops off substantially especially in a Daniels/Allen/Nate setting - and I want Perk in there to pick up that slack up.