Didn't the Haudenosaunee had a matriarchal system? Like, the faces of politics and war might have been men but the true power came from the women? If so, wouldn't it be wonderful to have them led by a woman, and get rid of the "steppe warrior" cliché we have from them and maybe having something more politic/diplomatic/builder? But I have few to none knowledge about Native Americans so I'm probably utterly wrong here.
Native americans societies being matriarchal is generally just another cliché. It has its roots in greek "ethnology". Making barbarians matriarchal was a way to make them more alien and inferior. That trope endured the centuries, especially in the minds of the jesuites who were filled with classical latin culture. The Jesuites had the monopoly on documenting so many cultures, which is both a sad thing since they were obviously biased, and a nice thing because so many other american cultures weren't documented at all, and at least the Jesuites were lovers of languages and systems, so they made grammars and lexica.
That being said, according to the jesuites (but keep in mind what I just wrote about them), the Haudenosaunee had a matrilineal society, meaning that land was owned (and worked) by the women, and the men had to move when they got married. The men were hunters, traders, warriors and leaders (though elected by the women, and though certain sources talk about a power alternance between men and women). The Jesuites justify the situation by saying that the men were often absent, so the women took their place (which is a rather patriarchal way to explain matrilineal societies).
Overall it's a complex topic, because while matrilineal societies seemed barbarians to the Jesuites, during the 20th century it became a proof of social modernity. For example, hippie culture started to claim that native americans had equal societies and sexual freedom. The issue there is not whether that's true or not - it's that it says much more about hippie culture and non-native americans in general than about people like the Haudenosaunee themselves.
Scientifically it can be quite hard to determine how their society was like exactly. The sources we have certainly tell that women had the right to speak and give their opinions, and that it's possible that the matrilineal society described by the Jesuites was a reality. But let's keep in mind that the situation in matrilineal societies is more complex than pure patriarchy/matriarchy. Even if women did own the lands and gave their opinions about who should be leader, the leaders we know of were still all men. If that means there was some kind of gender balance in society, we don't know. But we must be careful not to look at poorly documented societies of the past with tainted glasses that make us want them to be superior in certain ways. The sad truth is that european colonists just shattered their society and identity and it's really hard to know what it used to be like.
The trope of the "steppe warrior" is more easily beaten that the trope of the "wise indian" and it can be very tempting even for scientists today to make old native american societies much more "advanced' in their own eyes than documented evidence allows us to say.
It blows my mind we haven't got a single South Slavic civ in the entire history of the franchise. Somebody should give Firaxis an up-to-date map of the Balkans, I think the one they have is from before the 6th century, so they might not know there are Slavs there to begin with.
The funny thing is that this kind of map tends to be very speculative. Just because it's on a map doesn't mean it's very accurate. Especially when it comes to people who didn't write much and were still largely nomadic.
Sometimes maps depicting the 6th century have slavic people all over the place and it looks like they are dominating europe with their big homogeneic slavic blobs.
Even 9th century Bulgaria wasn't a south slavic ethnostate.
We don't have any representation of the region because it is divided, not well known, complicated to understand, and has not big enough fanbase to demand it. 
