This is driving me crazy as well! I stayed up all night, convinced I was on the verge of discovery. I even went as far as to replace every face in /charactercustomization/ just to check if they did something as crazy as baking hundreds of potential face textures (there are hundreds of human non ghoul/scorched faces for some reason). The only lead I've found is that the materials and the nifs for the head seem to point towards actors/customization/characters/basehuman(fe)male/ (might be slightly off, on phone so this is from memory) But I can't seem to find this directory or the referenced textures in -any- of the ba2s. I tried changing the paths in the nif and materials to reference the textures in the folder that's in the ba2s, I even tried packing the textures to be in the mysterious customization path. The game crashed when doing the former, so that means something interesting happened I guess. When I get home I'll try to do it properly with the updated fallout 4 material editor. It's just really really bizarre. I looked at every file I could find with names like basehuman, face, skin, head. I messed with all those files trying to get a result. Maybe we'll figure this out. At least I have someone to share in the suffering with.