Well further testing shows that it doesn't matter where the weapon is located on the map, but the attacking unit must be adjacent to the targeted unit for an attack to be applied. Now I am still working on how to apply wounds regardless of attack (using Urist Da Vinci's formulas), and indeed I have a working script for that, but it doesn't handle things like breaking a bone through a body part and into another body part, or any other fancy wound mechanics.
I wonder... I suppose I could make a copy of both attacker and defender off screen and next to each other, generate the attack, and then copy the wound from the simulated target to the real target. That would keep all the wound calculation on the same, in-game system, but allow for complex attacks. Of course it would also involve creating copies of attacker and defender for each such attack, and that might lead to it's own issues, not to mention erroneous reports/announcements. It's odd to me that firing/throwing an item has no associated action. I suppose once an item is turned into a projectile it is no longer a part of the action system and no behaves independently.
But I think, with the combined functionality of adding attacks to units, and simulating attacks using mathematical formulas, I should be able to come up with a decent, all around attacking system. Just have to test things out and see what the game thinks.