I already requested for the two large Native Groups in the Midwest to become nomadic governments. I request this because of 3 reasons. One, after the event that caused the apocalypse, the natives were free from the reservation system, it would make sense for them to continue their nomad way of life, instead of switching over to farming, which would breed feudalism. Secondly, Steely mentioned that the areas that are still tribal or nomad, stem from agriculturally poor land. The Midwest itself is especially hard to farm on, the natives didn't even try farming because it was too difficult and "settlers" themselves had a horrible time growing stuff in the plains, it was cold and there was too much wind, and there were even huge dust storms in the 1900's. In short it would be much easier to conduct a nomadic way of governance that relies on cattle and hunting, both of which eat grass, the most abundant thing there. And last but not least. It would spice up the game play, the nomads don't really survive in this mod, they usually end up getting wiped out by the Norse, the feudal Lakota, or they conglomerate into a single nomadic state. With the Comanche and the Lakota as Nomads, the Nomadic government would last longer without player support, and it would make the Midwest vastly more interesting.
TL;DR
#1: Nomadic Traditions
#2: Terrible farming conditions
#3: More interesting game play