"Also note that the Spanish are horribly outnumbered in the Battle of Otumba.... a good sign that Spanish / European troops will be superior to the Aztecs and the Aztecs need overwhelming numbers to win"

Maybe but the disparity in terms of basic troop quality is not as much as numbers alone suggest. For one thing most of the the Spanish units have 8 points of experience to the Aztecs' 2.

I find the statement that the HRE lacks professional units somewhat strange. That is, after all, where Landsknechts came from and it appears from screenshots that pikemen, doppelsoldners, musketeers and reiters are all available to the HRE.