I would love to see some Native American clans from Northern America (Turtle Island) be implemented into AOE IV. The Cherokee actually have a really interesting culture that could be captured very well within the AOE IV Universe. If you research the Native American people enough you will also find there are many more groups as as well. During the time period of which AOE IV is set they were waring with other clans on the continent. It isn’t out of that time period, it just comes down to if you want the game to be set around a certain province of the world.
In summary: You could have each of the clan systems of the Cherokee be implemented into their economy unique to the Cherokee, and utilize it for the Age up premise. Similar to how certain factions work where they aren’t restricted to just one choice or the other but there are unique design structures for the civ that allows many avenues for the group to take. For example, the Governor’s system from the Tughlaq Dynasty.
(Some stuff you can’t take literally from sources like Wiki, as with many sources of information in contemporary culture we must sort out the facts from the opinions. For example, the Native Americans never used the word “Chief” to describe anyone in their clans, and of course Wiki uses that word. This is just an example of things that when you research you need to be careful what you regard as fact. When gathering information I always prefer to hear it from the source rather than someone else who is telling me what they heard or think, even over written documents. Most of the stuff on that page seems relevant to this information though. Now we will have to also be aware of time stamped data with regard to videos since those to can be counterfeited nowadays.)