Horrible trade, makes absolutely no sense rebuilding wise...You get younger when you rebuild, not older...
.... well, it's not a rebuilding trade.
Pau's about the same age and has been in the league about the same number of years as KG was, back five years ago when we did that trade. Could argue that KG had more miles on him, since he played so many minutes. Making this trade would be about squeezing out the last couple years of Pierce, and probably re-signing Ray and KG this offseason (if you aren't trying to maximize cap space, you can keep their Bird rights). You'd forgo being a real player in free agency this summer, for being more relevant this year (and maybe next).
It *could* work out well. Trade for Pau, you've solved the center problem and greatly improved the rebounding/inside-out balance. No point guard, so you go hard after Nash this summer with whatever we can offer (New York needs him much less with Linsanity still going strong). Have to make some kind of deal for this season, though; Bradley's not going to cut it by himself, even with Paul playing point-forward.
Re-sign Bass to be the super-sub big, and re-sign Green (assuming medical clearance) to back up Pierce.
You COULD (without too many stretches of the imagination) go into the next couple seasons with a primary rotation:
Nash
Ray Allen/Bradley
Pierce/Jeff Green
KG/Bass/JJJ
Pau/Chris Wilcox
That's obviously one of the oldest teams in the league, but it's well-balanced, I think. You've got outside shooters, mid-range shooters, an inside presence, and Pierce's slashing/all-around game. You've got a few young legs in Bradley, Green, and JJJ. Still have two first-rounders, unless you need to use one to get a PG for this season. Maybe you can get LA's pick for taking on the older, more-expensive player.
You need a backup PG and another backup big. Same as every other summer.
But, isn't that a team that could compete next year? It's a lot more balanced than what we're putting out there now.
EDIT: If you can get a first-rounder from LA for taking on Pau's contract, those three picks can probably be packaged to move up a fair amount in the draft. You could either infuse a lot of young talent at the end of the roster... or maybe go after someone like Austin Rivers, for some bench scoring. But, that's a whole other discussion.