In addition to the AI issues (which are huge), and the player frustration issues (ditto), it's not even particularly realistic. Medieval commanders were absolutely capable of laying out battle plans across multiple fronts ahead of time. No, they didn't have the same level of instant control that we do, but they certainly can (and did) have things like "Duke of Lancaster, you go raid Normandy while my son raids Aquitaine (and using messengers to keep track of where they were and what they were doing at any given point)."
And having an entire battle plan interface is far more than any sane programming team would do for an optional game rule; that's a significant UI and AI project that would consume a lot of dev time and effort, and would be a major part of a DLC-level project.
And having an entire battle plan interface is far more than any sane programming team would do for an optional game rule; that's a significant UI and AI project that would consume a lot of dev time and effort, and would be a major part of a DLC-level project.