Now that I've figured how to handle edited meshes in NifSkope, I decided to play around with the Sculpting mode in Blender and remodel the male orc head. They now appear to have a stronger jaw, slightly bigger and sharper tusks and an angrier look on their face which should look more intimidating compared to how they originally looked with the Oblivion Character Overhaul V2 mod. Their mouth now appears slightly more closed, which should simultaneously give them a neutral expression.

Install:
Extract the "meshes" folder to your data folder and click Yes to overwrite.

Known issues:
The head mesh might clip through some of the hair meshes but it shouldn't be a big issue.

Also check out my two other mods which should work well along with this one:
Detailed Mouth for OCOv2
Lifelike Eye Normalmaps