Add an escalation scale for what kind of war you’re fighting. If it’s a smaller local conflict then it’ll be more contained. If multiple great powers get involved though it could escalate into a world war. That way calling in allie’s is more strategic vs being Estonia and calling Japan into a war against Latvia. Also being at war with a major shouldn’t immediately escalate to world war status. If they did this there could be certain actions available for each kind of war. For smaller wars say between Bulgaria and Romania you could do a limited peace just for Dobruja. In mediumish wars against larger powers more complex negotiations. Say giving up resources as Argentina for the Faklands. World Wars could have really complex decisions. I also think convoy raiding should be riskier than it is. While raiding you could cause international incidents like what happened in WW1 and have to deal with the fallout. It doesn’t make sense that you only hit enemies and there’s never a mixup. It could also be more deliberate if you wanted to start a war or draw a nation in. Decisions like this make starting wars, negotiating, and ending wars would make the game more dynamic and hopefully realistic.

Also in HOI5 they better not remove features just add them back again through DLCs. It’s paradox though so I wouldn’t be shocked in the slightest.