or maybe it is not possible at all

it is very easy, since mods can control (= change) who owns a territory at any point in the game. Calling a distribution mod would only have to be called once at the beginning of a game tho.

You could use custom scenarios... https://war.app/wiki/Custom_Scenario

custom scenarios are a last resort because I want to be able to rapidly generate new games
That said I have never done one so maybe it is time to get on that learning curve

Just make a custom scenario and make the settings into a template. That way you can make a game with those precise settings and same scenario in a matter of seconds.