Defensive lines

This idea is based on the supcom style of unit creation.
The idea is to create Defense lines instead of a simple move here command. The player would create a defense line where they would want units to guard. The formation of this line would be selected by the player( i.e. melee/front, range/mid, artillery/rear, etc.). Units in the line would then defend the line by either moving to the attacker or holding position, then returning the line. The player can then easily shift units on different lines by selecting units and moving them to a line or by having a unit creation building sending there units directly to a line.
I know alot of you would say, "Just use patrol". However, it's not the same thing. As units are assigned to the line they would be spread out to cover the entire line evenly. To do the same thing with patrol you would have to have numerous small groups doing short patrol to maintain a consistent line. In patrol mode units always get bunched up and you end up with clumps of units. Thanks for reading.
EDIT: Just read Webbie's post on population caps and this would work great if you are using a defensive line as a standing army. It would help control the size of the army and keep the player from creating and impenetrable wall of defense