Some User Interface proposals:
The Generals Menu should be more User friendly. if theres a General who is clearly better than another one, the better one should be able to be put on top of the list.
A button to automaticly expand factories.
A list for Provinces and buildings, where you can build them, just like in EU3.
Save the preferences for the Ctrl + 1 etc. shortcuts for selected Units in the save file. (actually not sure about it in Victoria 2 but in EU3 you had to put in the shortcuts every time again when you restarted the game.)
make it possible to decide after which time the small notices (the icons) on the side of your screen should automaticly disappear, so you don't have to click on every single one of them if you would prefer them to go away on themselves after some time.
On the Infrastructure Mapmode, it would be cool to see a certain colour for every stage the railroad has in every province. Right now you just see if its up to date, in the same beige colour over and over again. Would be cool to see it to progress from level 1 to maximum level and also see the colours of provinces outside your country aswell, so you can compare it. This information is public since you can see it when you click on a province outside your Country, and it would give more variaty to what could be an awesome indicator on how the advancement progresses in the world. Could be even as interesting as the political mapmode from an infrastructural point of view.
also, would it break the gamebalance if you would allow Regiments to recruit out of a region other than a single province? I think it could improve the mechanics of recruitment and manpower, but I'm not sure about the ingame consequences of this.
last but not least, would it possible to put the actual country name to the country tag in the savegame file? I'm sure I'm doing it wrong, but right now I have to search for example for the name of some prussian general, to find the non-human prussia in the save file. If it was just like the province names, it would be perfect.
sidenote: also some sort of Aggressive-AI button maybe could be fun too.
ps: would it be possible to create a sphere of influence worldmap where you can see the greatpowers and in whose sphere other countries are.
I think thats it, thanks!