That's kind of the idea. I think it would work nicely with the current LC. For example, right now on BT the sum I outlined above would sum up to (without naming the regions):
Region A: 4+4+8 = 16
Region B: 3+8+13 = 24
Region C: 3+13+13 = 29
A has two regions in the realm being looted, both in different duchies
B has 4 regions being looted one other being in the same duchy
C has 4 regions being looted, all in the same duchy
And I think BT provides a good worst-case scenario for looting of many regions right now. Divide by some number, substract a small "tolerance" value and we're there. Say, divide by 3 for morale, 4 for independence and 5 for loyalty and substract 2 as a tolerance and you end up with:
A: -3 / +2 / -1
B: -6 / +3 / -3
C: -8 / +5 / -4
Now for other islands, looting one region to the ground seems to be the more common strategy. There are far fewer regions on other islands being looted, but the individual LC values are higher, much higher. We might want to sum up sqrt() values instead.