I call this the "revamp" because we could still be competitive this season.
Pierce and Garnett could stay on, or they could retire at the end of the season. The Celtics would have acquired some young guys, and shaved a fair amount of money off the cap in the future.
Terry + Wilcox + 2nd round pick
for
Mozgov + Randolph + Fournier
http://espn.go.com/nba/tradeMachine?tradeId=a3lquxhRondo + Bass + Lee + Collins
for
Millsap + Kanter + Mo Williams + Foye
Mo Williams won't be back until March / April. Once he is, he can still be a valuable shooter and ball-handler, either as a starter or as a sixth man. Foye could man the point until then, and Barbosa can step up and play a larger role, too. The team can still hope to compete this season with more size and depth in the front-court and a major upgrade at PF.
The Celtics can decide in the off-season whether or not to keep Millsap. Kanter is a nice big man prospect at center. Mozgov is a solid backup center prospect -- that gives us three young seven footers at center to develop. Between the three of them we can hope to get a couple of quality players.
Why for Denver? They could use more quality depth and experience at backup SG. Fournier, Mozgov, and Randolph are all fringe rotation players for them in any case. Wilcox can do for them what Randolph can do, only he's smarter and more experienced.
Why for Utah?They get a point guard they can build around to pair with Favors (and Big Al, if they choose to keep him). Lee is a solid defensive SG to put next to Hayward, who is more of a scorer / shooter at SF. Bass can fill the role that Millsap played in the offense, though he's obviously not nearly as productive or effective.
Still, it seems like pretty decent value for them all things considered (seeing as both Millsap and Big Al could be gone this summer in free agency). Foye is a free agent to be as well.