Chi would definitely benefit from PP. It would block LeBron too how tempting....
Pierce makes 15.3 mil this year and 16.7 mil next year. Indiana has seemed like the best fit for a trade simply because they have 14 mil in cap space... so Pierce for Paul George straight up works (and George only makes 2.6 mil next year. Gives you another 14 mil in cap space to play with.
For Chicago it's a little trickier, i think. I don't see the point in taking back Deng for the same reason I don't see the point in taking back Granger or Rudy Gay. Pierce will remain better than them for the next couple years, but you'd be stuck paying these guys the same kind of money you'd be paying Pierce. SO why bother?... you're cap situation remains the same. I mean... MAYBE if you are absolutely convinced Deng/Granger or Rudy + Rondo would be enough to entice Dwight. Otherwise, the goal should remain finding expiring contracts + young players and draft picks. With Chicago you can do this:
Kyle Korver (5 mil) ... only 500k guaranteed next year so essentially an expiring contract.
CJ Watson (3.4 mil ) nothing guaranteed next year... basically an expiring contract
Ronnie Brewer (4.7 mil) nothing guaranteed next year so basically an expiring contract.
So that's your expiring contracts... Brewer, Korver and Watson are basically cap filler. You can cut them all ... doesn't matter. It frees up an addtional 16 mil in cap space next year so we'd have roughly 41 million in cap space to play with.
In order to make it "worth it" to the Celtics as anything more than just a straight "Cap dump" you need some kind of value back. So you obviously ask for Chicago's 1st rounder (which unfortunately will probably be pick #30... would rather have the first pick in the 2nd round than that pick) ... but the Bulls also own Bobcats' 2012 first-round pick (top 14 protected in 2012, top 12 protected in 2013, top 10 protected in 2014, top 8 protected in 2015, unprotected in 2016) (Tyrus Thomas trade 02-18-10) ...
Trading Pierce for a LAAAATE 1st rounder and that bobcats pick might not be worth it... but again, it goes into how "big picture" Ainge is willing to go with this. Maybe they get a 3rd team involved just so they can get another young asset out of it. Youngest player on the bulls is 22 year old Jimmy Butler (picked 30th)... Doubt Boston has much interest in him, but throw him in for the heck of if it