Back when I had my commodore 64 (I know, eons ago
) there were a series of games involving WWII that involved division to corps level command, however the individual units were battalions. What you did was give orders to your regiments like "attack," "defend," "support defense," "move to," ect, along with certain geographic objectives. The AI would then do so while doing its best to maintain the regiment as a cohesive unit (meaning that certain slower units included in the regiment would slow it down).However, you weren't able to give orders to your individual battalions, only to the regiments. Very realistic, because as a head of state, you aren't (or rather, you shouldn't) be concerned with the movements of battalions (or even divisions for that matter), unless you are micromanaging in the worst tradition of leaders.
I would also back this up with my playing experiences once I got to the later stages of SR 2010... I would simply mass a large quantity of armor and mechanized infantry and send it along the nearest road en masse towards the city I wanted to take. And I would succeed most of the time too. Far easier and more realistic to simply issue commands to combined arms Brigade Combat Groups that I have assembled.
Also, one other thing. The diplomacy hit for using nuclear weapons needs to go way down. When a nuclear power initiates first use, realistically they aren't going to have a bunch of other nuclear powers of equivelent size getting in line to declare war on them unless they don't have much of a nuclear arsenal anymore. Most nations wouldn't want to fight a nation that has already used nuclear weapons unless that nation is much weaker, or if that nation has used a significant portion of its deterrent. AI behavior at that point should be "stand back and see how weak the two belligerents become... then jump on them when they show weakness." Nuclear war isn't something most head of states are going to rush into.
That's no fun for us.