I actually disagree with you Matt.
Without getting into salary issues, trades, cap, etc etc,
and assuming this scenario is realistic, your reasoning assumes that you build teams like legos, and the players' expected performances are exactly or similar as they are with their current teams. Nothing further from the truth.
It goes along the lines of... Ray Allen is a great shooter, we play inside out, when other teams double team TD, Ray Allen will make them pay with his jumpshot. He would be awesome!
I heard similar things when Brent Barry became a Spurs not so long ago (and I am not comparing them, but I hope you catch my gist). Brent is a very intelligent basketball player with a soft touch and good guy. It was supposed that Tim Duncan would make him even better, right? All his numbers are down, he couldn't adapt to the current Spurs' system. What makes you believe any player can play under the current system and conditions?
What most people fail to realize is that Ray Allen needs the ball in his hands to be effective and a large number of FGA/g. In the last 3 years Allen has taken:
year FGA/g FG% 3P%
02-03 18.17 .439 .377
03-04 18.16 .440 .392
04-05 19.15 .428 .376
In this playoffs, Ray has taken:
year FGA/g FG% 3P%
04-05 19.54 .474 .378
If you expect Ray Allen to take a lesser role, you don't know him. I do not expect him to significantly reduce his touches. This implies two things...
1) Either Tony Parker drastically reduce the number of touches he gets.
2) The Spurs completely change their offense (increase the pace) to allow an increase on the number attempt per game (we become a running team).
Tim takes 18.22 FGA/g and Tony 16.5 FGA/g. They both take the most FGA/g on the Spurs team. People still don't realize that Manu is having this increadible run while taking only 12.5 FGA/g and without significantly changing the Spurs offense. This is what is the most remarkable aspect of his performance, and I can guarantee that NO other player in the league can perform as well as he had in the playoffs with the limited touches and role given to him by Pop. NONE!