Suggestion:
I've been reading up and thinking a bit about this... What would be really cool, and quite viable is this:
We get a GUI for administration of your staff. In this GUI you start top down, and choose for example a field marshal. Next to your field marshal you get a check box where you can choose if he can pick his own generals, or if you want to assign them to him. You also get a slider for how many officers he gets from each level below him. In addition you can give him controll over officers from other weapon braches.
Also, and this is important, you get a slider that defines his degrees of freedom... that is.. how many provinses he has to work with when making his plan.. for example 10 provinses off the axis... Later, when you assign him a axis, he knows that there are limits to the field of operation. An air marshal could perhaps get 50.
This same system can be applied to lower officers.. you could put a general on top, and define de same parameters. A general could for examlpe get 6 degrees of freedom.
Next thing you do is to assign troops to the different commands. This is done in a separate GUI, where you get a graphical overwiev over where troops are and who they are assigned to.. Once assigned the appropriate officer starts giving orders on where he wants his forces.
To achive the assigning axis part, we will need a way to communicate battle plans to your staff. This should be done in a battleplan gui, where you can set up defensive fronts, offensive fronts, objectives, axis of attack and areas of envelopment. If you plan a retreat, you also want to give your staff an axis to retreat on. Also, perhaps a time table and some sort of degrees of freedom here aswell.
The implication of this is that there must be several AIs working together. The field marshal gets an AI, the generals underneath him gets their AI and so on. AIs controlling other AIs. Another implication of this is that there needs to be an AI that communicate partial battleplans to lower staff, for them to execute.
I think I have seen a version of this somewhere. I think it was empire earth 3 where you could send battleplans to your allies. Also, diplomacy has a way of sending battleplans to your allies.