I've seen lots of good ideas and thoughts here on this, and I'll just add my two cents:
Boston teams of the KG era have been built on defense, and I think it would be wise to continue in this vein. Also, Boston needs to improve in the rebounding department. In light of these two elements, it seems to me that 1) trading Bradley AND Lee is a bad idea; we need to keep at least one of them; 2) acquiring a rebounder/post presence of Gortat's caliber, if given the opportunity, should be given serious consideration; and 3) Boston should hang onto someone it already has who has such promise as a rebounder (Sullinger).
I like our current team, including Green and Bass, but if this team is serious about winning NOW, it should use its surplus (guards and undersized forwards) to address what it still needs (legit bigs and rebounders), so if Danny can turn AB (or Lee), Bass (or Green), Melo, and a first into Gortat and filler, he should do it.
This would leave Boston with a legit frontcourt rotation of KG, Gortat, Wilcox, and Sully, plus a solid backcourt of Rondo, Terry, Barbosa, and Bradley (or Lee). The only possible downside is not having a legit 3 to back up Pierce, but maybe Lee could play some there (if he's not traded), or that need could be addressed another way.
I just don't think smallball is going to work, and that the best chance of beating Miami (and the Western champ) is being big and bruising inside. Rondo can handle Chalmers, sic Bradley (or Lee) on Wade, Pierce defends LeBron as well as anybody, and follow a strategy of being tough and athletic in the paint with KG, Gortat, Wilcox, and Sully.
This also sets up Boston well going forward, with Rondo at point, AB or Lee at the 2, Gortat at center, and Sully at the 4. That's a solid young nucleus to build around.