Perhaps a system whereby you can micro-manage an individual attack on a province in basic form? Default would be AI control of the attack (basically what we have now), but the option could be given to focus your tank spearhead on the right side of the province, and infantry support, while you send another division to attack on the left to tie up enemy defences. We're talking about quite a while in the future though because, obviously, the technical implications of this would be quite large
Would add a larger sense of control when fighting real important battles such as city sieges, or pivotal battles along your spearhead, hence why the default would be set to the standard current form where a "generic" attack is made. As a result, micromanagement wouldn't be an issue. We would however, need an AI that could deal with it, as you essentially add a 2nd layer to the AI; the strategic level which is currently existing, and the new general "tactical" (really it's still strategic but a bit more zoomed in) AI. Perhaps you could also achieve this idea by splitting individual provinces into further hexes/sections (that appear when you zoom in further onto a province) to perform these manoeuvres, with the movements done at brigade rather than divisional level. Not only would this add greater immersion, but it would also be much more fun seeing your brigades attempt to fight through the city sections of Stalingrad as opposed to divisions attempting to just attack the city.
This idea would enable a "free map", whilst not taking away from what HOI really is or adding any sort of extra micro burden on the player.
Personally I think this idea I just came up with it much more effective than my idea earlier. Would people be in favour of such a system? (for hoi 4 or 5)