If there is going to be an expansion, here are my ideas
- I would add in factional alliances (aka country blocks) for major and secondary powers (make sure it is highly moddable though, I could see it ending very badly for the mod I am working on, divergences, if you dont!) like hearts of iron, with several levels, such as guarantees of independence, integral (will automatically join if you are attacked) and membership (regular). So WW1 would be represented at the start by an integral alliance between france and russia with russia guaranteeing serbia, with GB being a member. The central powers would be represented by german and austrian integral membership with the ottomans and italians simply being members. Austria attacks serbia, france and russia join, germany joins, italy dishonours the call, the ottomans join in along with GB, and as the war goes on countries shift toward the allies and join in. You would have to factor in things such as influence into the system, and this would go along with a general rework of the system, but remember, moddablity is key! The blocks can be abolished and created by any GP, though, the rest are just regular alliances/vassal stuff
- A rework of infamy, rather than being one arbitrary number, make is based around a limit to how fast countries can grow with integration into the factional alliance system, if you play as germany, and take all of austria and european russia in one war, a country block of all your former enemies is going to form to beat you back, the ottomans, british, french, italians, americans, and what remains of austria and russia are all going to dogpile to try and reduce you in size.
-Cores vs claims, enough said, think greater italy, and ottoman europe.
-Military rework, with trench warfare taking place, and it just not being attack vs defens, planes that do plane stuff, tanks that destroy, so on, the current system works early on, but it makes less and less sense as the game progresses.
-Moddability, make sure tiggers work, release a list of commands, and other triggers requested by major modders such as rylock and nas. But make sure pop commands work, most of all, especially the culture change command, it would make modding so much easier
-Fix vassals, nuf said
-Try to get as good of an Ai as possible, I know its difficult to programme a good ai, but the ai right now can barely manage a country split in two by a body of water