There are a lot of things to bring up to speed like making the Nootka Warchief a hero, giving Cheyenne a dog soldier unit (either an addition or replacement), and making Tupi Poison Arrow Frogs actually grant poison damage.
Some generic native upgrades could also help flesh out the lacking tribes and be easier to learn since you’d encounter them more often. For example, an upgrade like Yoruba Herbalism is generic enough to just be Herbalism and be available from a variety of tribes.
The map locations of many of the tribes also need a major rework since many of them are very inaccurate.