Could you make a tweak to the ToItem attribute on damageAlter? Currently, it goes through items one at a time, damaging it until it destroys that item. I can't see a good way to use this functionality. It randomly destroys an almost-fixed number of items, regardless of how many items are on the unit(s) hit by the attack.
I propose that ToItem causes all items held by the attacked unit(s) to be hit the same as if they were on the ground. This means, for example, that a ToItem value of 1.0 on an explosive would destroy items held by units just as though they were laying on the ground.
If the current functionality of ToItem is worth maintaining, then I propose a new value: ToAllItems