If this is already mentioned before sorry, but I got this idea a while watching my soldiers sitting still in the defend area.
Idea: The “soldiers” (knights, archers, footman and Clerics) when they leave the main area to defend a position they should build a defend able area to work from.
Reasoning: When you look through history when ever an unit settled down for the night they always set up something to where they were not left sitting in the open. The Romans built little modular camps that could be done in an hour or two.
Suggestion: Have the Mechanic build something that the army could bring with them, maybe a wagon that has to have a worker assigned to the group to pull. Then when you tell a unit to defend an area the footman then pulls stuff out of the wagon and starts building the structures. What I was thinking for what should be there is a Fire pit for them to sit around, tents (make them function like beds but not as good), crate (for food), fences or something to function as walls.
Here is a bad drawing of the Idea you would just mirror the rest on the other side:
= fence Gate
F= fire pit
XXXXX---XXXXX X X X T T X X T T X X X - - - F -
As for the workers involved.
Taylor: Canvas for tent or maybe even build them
Mechanic: Build Tents, wagon, and Covered wagon ( wagon with everything in it)
Cook: Food maybe adding a Ration type thing as a meal.
Mason: Fire pit
carpenter: Fences and fence gate
Sorry this Idea come out so late in the games development and it may not be do able, but thank you for taking time to look at my suggestion.