They should make tribal nations more like the Natives. You don't control a country, just a group of natives. They can peacefully live on another country's land, or they can invade and set up actual states for themselves. If they don't have their own state, you can send natives from province to province, just like troops, in order to simulate migration.
This might not be so useful for the actual EUII scenarios as for earlier scenarios, but that would be so cool
This might not be so useful for the actual EUII scenarios as for earlier scenarios, but that would be so cool