Game idea: Make Vassals different levels from lvl 1 to 3. Lvl 1 you only have control of who they are at war with and you can store your army at their terretory. Lvl 2 you also Have your country in their name like "brittish Netherlands" plus that you get 25% of their money and resource income. Lvl 3 is when you get half of their Income and they have the same color like your nation and they have the same flag like you( flags should be added when you click on a country). Make sure that in order for a vassal to become independent they need to declare war and make an agreement. Also rename vassals to puppet states cuz it's just a better name.)