How is it ahistoric to punish expansion and war? You can count on no hands how many people in the CK2 time period successfully conquered Europe. It should be harder for players to do it. You know what I felt the first time I successfully painted every province in the game my color? Satisfaction. Not pride. Just satisfaction. I want to reconquer the Pride I felt when I first united Ireland. When I first formed the Empire of Britannia. When I first won Jerusalem as a goody prize for a Crusade. When I first defended Jerusalem from a Jihad....
I want to face a challenge again, and feel pride at overcoming it.
It's ahistoric due to the fact that coalitions were not prevalent at all in the time period, war was commonplace. Historically, some far Muslim ruler wont join a coalition to help some far Catholic ruler. With the coalition mechanic, we'll see completely contradictory coalitions of members in far away realms, different religions and ideologies. This is the main immersion killer I'm referring to, Its going to devolve into a gamey tactic and thats the issue. Secondly, it shouldnt be harder for players to go to war, I think the difficulty in war is already fair. It should be harder for users to manage their realm. Keeping vassals happy, keeping peasants happy, keeping claimants happy, keeping family happy, keeping the religion at a respectable level (when applicable) should be the way in which difficulty ramps up in managing large realms. Revolt risk should be greater in larger realms, heresies should be more prevalent, vassals should be harder to keep content (which is happening in conclave), claimants are always a danger as we know, and should have a few more special events to trigger claims in unique ways. Realm and vassal management is the way in which difficulty should ramp up, restricting war is the wrong approach.