One thing that is overlooked is how colonies from different kingdoms interact. Real world colonies were well-fortified to defend against privateers, pirates, and the possibility of war with another European nation. In the 1600's conflict was mostly raiding, but by the 1700's, armies fought in the colonies whenever a war erupted between the home countries. Also, often times natives were courted to fight against other colonies in return for assistance in the form of goods, weapons, and help against other tribes. As your native nations are more powerful, they could be a serious potential factor in such wars, and would have a lot of diplomats visiting in the name of their ruler. Since this game seems about colonizing, you definitely need to flesh out each colony individually, as even colonies of the same power are going to end up different based on the value of their exports.