Whenever a nation occupied a territory, there would be a small chance of getting an event of War Crimes. An option to keep quiet about it might raise a small bit of CON, but would reduce the chances of a peaceful GP hearing about it (which would again just have a small chance of happening).
- Submarine warfare, if implemented, or blockades in general could have an event chain:
-- Blockader: Unrestricted Naval Warfare? War exhaustion rises in the enemy if they do this, or maybe a prestige loss if they back down from the plan.
-- If they choose to enforce this, peaceful GPs would occasionally get events: Peaceful Ship Sunk! Which would lower relations with the blockader.