odd harness
What if there was a system that's every few months the environment changes like seasonals, this making it so armies that aren't used to cold have a disadvantage. The only way to counter this would be with a supply menu that allows you to buy supplies for your troops so you can make different divisions for different environments (example: you get winter clothes for soldiers that are meant for cold areas) thus spicing the game up even more.
Also there is a system which makes vassals, this can be done when the country is weakened and is at your overall mercy, you can select it and press "vassal" (which would be a chain symbol),
Pros:
You get more income
You can get troops from there
Puppets/vassals will help fight with you
Cons:
They might uprise
Old allies will attempt to liberate a vassal
Final recommendation would be liberation, this sort of ties into the vassal thing, but can be used without it. Nations that are taken over can be liberated giving them the same government as you, making them your ally, and improves relations.
hot obsidian
hoary wing