Very quick idea for feedback.
Right now, there's no reason to shoot a non-Nemesis NPC anywhere but the least armored location. There's also no major benefit to getting a headshot.
So here is my super simple idea:
On non-Nemesis NPCs, the following rules apply:
If you hit the Head, double all damage after Soak.
If you hit a limb, halve all damage after Soak.
Voila. What do you think?