A bit late here, I know, but:
America: Minuteman, and replaces rifleman. And perhaps abandon the SEAL (use that for a sort of commando unit in the mod) and the gunship as the other UU then.
Germany: Definitely the Teutonic knight!
France: Torn with the Dragonder unit showed, because French paladins where more famous in their time.
Spain: I would make the explorer unit into a unique spanish unit instead of the galleon showed. Make it switch with the maceman. That reskinned galleon could perhaps be a better naval combat unit. Somethink akin as the ship of the line over frigates.
Aztec: If it would exist, a reskinned version of the spearman (let's call it an Eagle warrior) with better defense in jungle while your elite Jaguar fits the more advanced role.
Inca: How about using the native archer as a first unique unit and the Quecha as a swordsman replacement as you envisioned?
http://forums.civfanatics.com/showthread.php?t=153700
Thing is, for Inca and Aztec, that atm they have the same unit twice over. I think it's much more interesting to have quite distinct UU's if you want to have 2/civ.