I agree with those saying that Alexander wouldn't fit well with Greece's civ abilities; I also agree with those saying that adding Macedon is a complete waste of a civ when the Balkans are already overrepresented, even ignoring the fact that Europe as a whole is overrepresented (NB: I want more European civs...later, when we have more non-European civs). I could have blithely lived without seeing the return of Alexander the Great; just make him a great general and be done with it. Same with Napoleon. And Genghis Khan. (Mongolia can have Kublai Khan.)
All that being said, I do admit that Macedon fits a niche not currently present in the game: single-minded rampant conquest. I'm not sure I would have chosen Macedon to fill that niche, however; after all, Alexander's empire crumbled immediately upon his death. I'd much rather have the Mongols fill that role. On the plus side, maybe we'll see a more nuanced depiction of the Mongols? The Yuan did make significant contributions to trade and culture, after all.