I am very interested in the mechanics of this as well.
Ideally, I would like to make a motorized mortar team that can:
Move - Mount unarmed hunters or some other appropriate vehicle, travel to firing point, set up
Shoot - accept and fire missions from the player
Resupply - either have resupply sent to the mortar team or have them travel to a resupply point.
If you still have this, I would like to see it. I am very fond of the DUWS mission, where enemy areas are dynamically created and the player can attack them. The support is just shells, however, I think it would be great to have a high command mortar team that has to be in place before fire support is available.