You should make a game about The New World(America). Where you start right before the Spanish arrive. You should be able to chose from many native American faction like Aztec, Maya, Apaches, Iroquois, Huron, Lakota and other old and new tribes. The time should go faster than any of the other games perhaps a week/month instead of a day to make the player able to play the whole story of America. It should be a bit hard to get and use gunpowder weapons but easier for the new factions(see below)
The old factions(Aztec, Maya) should start off well against the Europeans but be more and more crippled when better gunpowder weapons comes to the market and by their fear for horses. The Aztec leaders should be able to control more forces.
The new factions(Iroquois, Lakota) should be better at mastering the gunpowder weapons but be vulnerable at the start because of their limited size of their empire/country and armor. They should also be good at riding horses
You should start with armor and weapons designed to fit that particularity tribe like Aztec should have animal fur armor and obsidian blade and trowing spears and wooden shields, and Apaches should have very little armor perhaps a wooden breastplate and tomahawk/war club and bow. The European forces should arrive be sea and from villages and towns captured from native Americans. Their should be no boats to be used by European forces. The Europeans should drop more and more away from armor and get better and better weapons. The Spanish should at start wear armor like that of a conquistador and new forces losing more and more armor until it is only clothing like cowboys.
You should yourself arm your troops with armor and weapons, you must be able to make the most basic weapons of your tribe like bow and war club. You should not be forced to join your starting tribe but you should have better relations with them. Tribes should be able to join one another and also join the Europeans, like the Tlaxcalans joined the Spanish against the Aztec and the Iroquois that joined the British against the French. There should be many small factions that are there but you will not be able to play them and they should only control one village.
USA and Mexico and other emerging states should also appear but I am not totally sure how that will happen, but it could be a way that a new city just came out of nowhere and belonged to that faction. Or if the city became very unhappy with is leader.
The tactics have to be improved to conduct such things as ambushes. Ambushes was one of the most used native American tactics. You should have a map of Middle and North America together. There should be many cities but it was only the Aztec and Maya and other old factions that made walls. The Iroquois and Huron did not make walls, in cases they would make a thin wooden wall. They should not have walls on their cities but if they conquered one with one the wall would stay there. You should be able to buy only native American weapons until late in the game. Horses have to be bought or stolen from European armies
Greetings from a Mount and Blade fan
