Inspired by (copied and edited) the "Coring Buttom" and the "Realistic Occupation Laws" mods, introducing Lebrensraum.
This mod allows for resettlment of an occupied states' population to allow you to spend political power to turn them into cores. Imagine the occupied country's population is being killed, and being replaced by your people to resettle these lands as core territory. You get to make "summer camps".
What does it do?
If you are a fascist country, setting your occupation law to brutal oppression decreases the occupied country's population over time, even displaying how many civillians you oofed. After a state has been reduced to 500,000 people or less (or if it is already at that amount), you can spend 100 political power to core the state. The option to core the state only appears once the state is below 500,000 population (assuming you annexed the state).
Seems to work, just in new games. It seems broken in existing games.
Also to simulate realistic civilian deaths from a tough occupation as well as forced labor in work camps but not straight up making c*oncentration c*amps, other occupation laws work to decrease the population by a little amount.