I'm also looking into the promotions...
Since the buttons for promotion are moved around depending on the unit's existing buttons, I'm guessing that you do not have to specify where a new button for a new promotion would go. However, where would you add a new promotion graphic, how would you link to it, and can you animate it (or not animate it) anyway you want? (i.e., discarding the "glowing" around the button.)
BTW, where are the units classed into mounted, armored, gunpowder, melee, etc.?
Thanks. I'm hoping I can help a little more than I could with Civ3.
Oh. Also, is there a place where the effects of the non-quantative promotions are defined? Things like blitz and amphibious assault. Is it possible to add entire new effects to promotions? It would be interesting if you could add a sacrifice promotion like the Aztec scenario in Civ3 or if you could create units that spread culture as a promotion.