With regards to army management, (this is not auto-management though) one improvement I can think of is to have an option to seperate stacks into tactical units. This is what I do manually (a lot!) and I think it would help many users if not most.
Normally in peace time I 'park' and in war time maneuver military units in relatively small stacks or tactical units, which I call brigades. Each of those can 'fight' on their own - what I typically use is 8 inf + 4cav per brigade initially and 16 inf + 8 cav in late game. This is a force large enough to remove most rebel armies but not big enough to fight (main) enemy's main stacks. Obviously for the main fights many brigades converge in one of my border provinces, combine to a single unit, follow & fight enemy stacks, then re-organise into brigades. Now at this stage, it would be great to have a 'un-combine' button, seperating say 60+ units into as many as possible brigades.
I don't know how other people manage their armies and don't want to believe everyone uses the same size or style, but due to game concepts I assume many people use similar park & move separate AND fight combined system? If so, this 'un-combine' button might save a lot of time, as I find this is the main repeatitive job while playing the game.
Programmatically I imagine there could be a typical 'brigade' setting somewhere, so that un-combine button would know how to do that, so any user can set their typical army composition in this setting once and use it repeatedly over centuries.
As this is related to army management, I would also like to hear about how you manage your armies, is there a better method that works for you, without requiring any changes to the game?
Thanks