I imagine the battleplan system would mean we need to plan offensives and defenses in advance. As it is, setting your units on AI control already somewhat represents this.
The issue here though is the medium. Because it is a game and we can give direct orders not as the head of state but rather some semi omnicient diety, we can change things on a whim. If, for example, the different generals wpild have personality traits that determined their willingness to go along with some plan (i.e. Something that modified their ai), if there were an org penalty for changing orders from the top (ie, you, the player) then I cam see this being a more realistic prospect.
Example. Imagime ypu draw up a plan that has Army A go through provinces x,y,and z to capture a victory point and set up a line. If you put an the personality of your commander, plus doctrines, etc, should determine the likelyhood of him retreating or pursueing the battleplan. If you decide to change orders afterr you have "executed" the plan, then their should be an org penalty proportional to the magnitude of the change.
Furthrmore, imagine if you had a little bar that filled up as the order cam to fuller fruition. When you hit certain player defined "checkpoints" ypu would get a notice from your general letting ypu know when to activate the next phase. Everytime uou complete a checkpoint your units get a small temporary org regain. However, to initialize the next phase requires a "readiness" meter to be buolt up. If you execute the phase with less tjan optimal readiness you lose prpportional org (this also applies to phase one)