Hang on...
Even if this WERE possible cap wise (which as far as I can see it is not), why on earth would Boston do this trade?
1. Humphreys is a better player than Haslem is right now - no basketball benefit
2. Humphreys is a $12M expriring contract - no fiancial benefit
3. Boston has too many PF's and may trade Hump to reduce logjam - Haslem is a PF. No roster benefit.
The only reason that makes any sense is if Boston did this intentionally to make the team worse, and no other reason. Or if Miami added another asset of some value (Oden, Ray, picks).
The base trade on it's own makes about as much sense as the Knicks trading Carmello for Jeff Green straight up.
I.e. none.