I think a method allowing players to queue up orders to units/groups would be a great thing, much like how you can queue waypoints. For example, sending a group of cavalry to move to point A, capture tower at point B, then move to C city. Or sending group A of workers to drop off food at city B, then moving back to the home city.
On the same train of thought, I think an "orders completed" notification would be nice as well. Many times have I sent slaves escorted by cavalry to build a mine, only to be reminded later when said cavalry runs out of food while sitting in front of the mine.
Thanks for your consideration. :)