I hope this game doesn't lose performance as the game progresses, with EU3 (HTTT) it becomes all but unplayable after about 200 to 300 years of gameplay because it simply gets slow.
I'd like to see a decent editor to help make mods (and sanity check them), I've seen way too many problems with mods.
Please, Please, pretty please do use a binary format (that can be opened by the editor and has perhaps an open standard if people want to roll their own editors) for game files and of course the save games and then zip those files. I have save games of over one hundred megabytes, which could easily be zipped to something less than 5 megabytes.
More realistic colonization would be nice, something like a colonial race where you vie with several other colonizers over a single province until you either win or lose. The EU3 HTTT manhattan province was irl colonized by the Dutch, English and I believe even the Swedish before it became part of the New England colonies.
Please at least test whether this game runs under wine. So far I have had great experience running EU3 as well as HOI under wine, it'd be a shame if EUIV would not work. (I realize asking you to develop this game for linux as well is probably too much, that's why I ask at least the testing under wine)
Interesting governments where you have more or less control over the people in your cabinet depending on how democratic your government is. For example, for a modern 'democracy' like Sweden or Germany the player has barely any influence over the cabinet whereas in a highly despotic monarchy the player has full control.
Automization of as much as possible, for example provincial decisions. When you have a small nation you want to manage these yourselves but with a large empire that's simply to much micromanaging.
Allow us to set things like the amount of times the game checks for events and such things, if the game performs badly this might make a world of difference.
Allow us to set what kind of engine-provided functions we do or do not wish to use akin to how openTTD manages its patches. I really disliked the cascading alliances which is the primary reason I'm stuck with HTTT even though I bought DW and it has some great features.
The horde mechanism as it is in DW is perfect for colonizing native territories in the US. Please use a similar mechanism. Don't use it for the hordes in Asia though.
It would be nice to be able to change flags and such from .pngs on disc during the game, nations as well.
I'd like to be able to have even smaller provinces to simulate city states, I realize it was possible in HTTT but very hard to actually use because of mis-clicking.
Joining of provinces to make bigger provinces. Suppose you have an empire stretching the entirety of europe, you'd want to join up the small provinces of for example the Netherlands to ease managing them.
Allow nations to 'request joining a nation'. This would be great to simulate events such as Texas joining the USA.
Allow us to have a standard response to events and simply stop showing pop-ups of these events. This I'd like to be able to set globally over all my games or in a single game. There are many events for which I take the same option every time except perhaps in early game. Having to click a couple of these away every month is a nuisance.
NO MORE REBELS PLEASE. I'd like to see a more realistic system where from time to time, if conditions are right, there can be a major revolt in which a significant part of the nation participates. Think of the Dutch revolution in order to get freed from spain. These should not happen too often, just often enough to make the game interesting and fun. It will allow smarter positioning of armies, you could put them all on the border with Spain for example because you don't expect a revolution and don't need to whack-a-rebel. If then the rebellion does happen it's more akin to a war then anything else.
Dynamic country generation based on cultures and possibly history. This would allow, in conjunction with the better rebellions as mentioned above, to create awesome civil wars akin to the one in the US where a part of the nation simply splits off. In EU3 this is impossible without having said generation pre-made. If the game can generate such countries and use names from a list of potential names (and if that isn't enough let either the player name it or use a list from the internet that already has player-created names), these civil wars become possible anywhere and will make the game extremely interesting in such events.
Use different infamies for different cultures and/or religion. When a European nation uses the Holy War CB it should give it very little infamy to nations of its religion, but should still give the full count to nations with the same religion as the defender.
Give each province multiple religions and cultures, the player must decide how to cope with multiple religions and cultures. Whether to exterminate them, oppress them, or openly receive them should be an important factor in the game as it was in history (think of the oppression of the jews). When cultures mix new cultures could be created, it doesn't matter if these haven't a real name (theplayer could decide to name them though), or just an identifier with which we can determine it's history.
Colonies should not necessarily have the same religion as the parent-nation, they usually didn't in real life either.
Save history apart from the save games, this will allow the player to disable history in order to increase performance. There could also be multiple levels of history-saving to suit what the player would like to store.
Allow a storybook creation in which the player writes his own 'diaries' to historic events and allow these to be easily published on a paradox site. It would make AAR-writing very interesting and fun in a completely new way. The game would also become more fun for the people that like to do it because you're really getting into the story of history for your nation.
It would be absolutely, incredibly, awesome if we could script our own AIs to complement the ones provided by Paradox. I'm not saying the Paradox AIs are bad, but it would be great if the game would choose different AIs for different countries every time you start a new game, giving every nation its own character. AIs that are downloaded from the internet could be unstable of course, allow the player to choose to download AIs himself or automatically. And in case of automatical downloads, use some sort of rating system that takes into account the ratings players give the AI and the amount of times the AI crashes.
Please try to run AIs in a group of threads, I don't know if this is where the problem lies with performance in HTTT. Running AIs in groups of threads, with as many threads as there are logical processors (or as many as the player will allow), might just give great performance.
Make it possible for AIs to actually make decisions on events based on their countries current status instead of just randomizing things. A smaller nation can handle a stab-hit better than a larger nation for example.
Please don't make the nationalism RR time-based but based on several factors of the province, for example, whether the people are better off in your nation that in their own.
It would be nice if instead of having 5 diplomats a player would have embassies in other nations and can communicate with every nation once every so many days, dependent on factors such as distance between capitals and how quickly a runner could move between the provinces.
The possibility of randomizing maps would be nice, not very important though.
It would be nice if the engine could use different forms of date (such as arabic, gregorian, julian, chinese). The support for negative dates would be nice as well for modding.
A better simulation of Federal and Confederal governments would be nice, not very important though.
Resupplying certain stacks more quickly then others would be nice. Resupplying a stack far from the line of battle can be pretty pointless.
Please no more PTI, I want to conquer the world, not just a significant part of it.