Got distracted there for a while so things ran on for more than half a day. Still, this is the last update.
Just to round things out I added in melee. Very simply when a unit activates it scans for adjacent enemy units and then distributes its melee attack across them. By rights it should also lock movement, but that's for another time.
The end result is a skeleton for a more advanced system. At the moment there are no real rules, but I've tried to use a modular system that would make it easier to expand. The visuals are also more at the abstract end of the spectrum, but they could be replaced with small figures or, maybe in an OpenSim megaregion, full-size models.