People allways want more and more, but still it should remain compact enough so new people aren't daunted about a massive amounth of data that they need to go through (like Victoria and Supreme ruler 2010/2020).
Basicly I want to have a lot of options to tweak with, but I think much of it can be automated without it really affecting your country's performance (in a bad way that is).
Some things I'd like myself to be added in-game.
- Evolving recources: Recources are pretty much set in stone at the start, techs and events can change them, but in general thats about all, perhaps giving the player the ability to administrate resource production on provinces up to a certain degree.
- The idea that battles could influence dissent/politics would be very interested, however I think it should have an "OFF switch".
- The idea about more permanent effects of war weariness/damage should be displayed in several ways damage to infrastructure/factories should be harder to "recover" from, there sould be a "manpower" counter and a "population" counter (manpower basicly is the available manpower for militairy recuitment, while "Population" the available "workforce"
* Manpower basicly provides military recruits (and reserves can count partly as workforce [say 50% efectiveness])
* workforce influences things like resource production and IC (effectiveness decreases from a certain point however) and both values influence manpower/workforce growth.
* Additionally both manpower and workforce should be stats that can be affected by things like stratigic bombing, nuke attacks, etc.
* Both values are regulated by a specific slider government policies and events.
* natural things like famine, poverty, etc.. should allso have some effect here.
- Make sea battles a bit more fun, sea combat is still a bit dull here it has some nice bits but theres still alot of improvement here make capital raiders effective without escort and escorts more suited when engaging anti-sub warfare, sea defense, make subs "less visible", etc..
- Evolving research: personally I think tech teams should gain experience while they research stuff which in turn improves their research speed/effectiveness, furthermore tech teams should have some profficiency in every type of research, but not all have the same value (and experience is gained in that area when a tech team completes a tech in which these areas are used according to the difficulty, but some random factor should be added as well [to add, a "decay" factor should be added as well], furthermore make some tech teams "randomly" pop up to give more flixibility to smaller countries.)
- The espionage stuff, personally I wasn't too excited about this, but it has its nice bits, perhaps let the espionage system work a bit more like the research model, with individual spies with their own strenghts weaknesses, etc...
Okay this is about the first I could come upon, there's lots more in here, but too much to name atm, but one thing thats most important for HOI3 is, give it alot of depth, but keep it simple enough to manage.
HOI2 had a splendid balance of this, it could have used some more depth, but all in all this barely was anything close of an issue.