I want to do some edits to a head mesh, but I don't know how to get it to export and work correctly after all the edits are done. I have done some armor mesh edits in the past where I delete the skeleton the imported mesh comes with, apply update changes, and re-import the skeleton, parenting it to the edited mesh, but I've tried head meshes before with no success.

Could anyone give me a few pointers how to re-rig a head mesh & skeleton, in Blender?

For head meshes, due to the requirement of their vertex order and count to stay exactly the same as in the fitting EGM (shape morph) and TRI (facial animation morph) files, you will already be screwed right from the start, if you import or export from or to NIF. This will resort the vertices and you can scrap the EGM and TRI files. (Recreating them currently requires around 80 meshes to be created from scratch, 1 for each morph applied to its fullest and for several of the face parts in conjunction, to then create new EGM and TRI files from these. NifTools im-/export scripts are still missing TRI file support, EGM alone is useless for editing head meshes.)

The way around this is through export from NifSkope into OBJ, then importing this into Blender with the option checked to keep vertex order intact. If you then manage to only use deformations which won't alter the order or count of vertices, thus none of the scripted tools, (also no changes to UV-maps = texture mapping layout), and export into OBJ again with the same option checked, you actually managed to modify the head mesh without breaking it.

Re-rigging is a different story, something I haven't yet tried myself admittedly. There are ways to position and orient the head mesh in Blender so it aligns to the rest of the body and perhaps could be rigged to the skeleton again (something along the lines of not moving in Edit Mode but in Object Mode, similar to what is done to head meshes in NifSkope, so the actual vertices keep their coordinates relative to 0 and the morphs can be applied, but they "appear" to be right on the top of the neck instead of in the center of the scene turned to the side), but never try to "join" it to the upperbody to even out alignment issues at the neckline or anything, as this 100% breaks the vertex order!

I'm sorry I can't be of more help with this.

Well at least you gave an answer which itself is appreciated. The "edit" I was trying to do was changing the NiTexturingProperty's "Apply Mode" of the mesh. If I simply try to do it in Nifskope, no results take effect. So I was thinking that perhaps importing it into Blender after changing the "Apply Mode" and re-rigging it might get the change to take effect, but no dice I guess. You at least helped me to see how futile it might be to try.

Thanks for the reply.

Well, the apply mode of the texture is a completely different story. It isn't taken over you say? Then that's just another property under control by the game engine.
Assigned textures on body meshes are overridden with the respective race's ones, defined by the material being "skin" and the name of the NiTriShapes/Strips containing one of the engine keywords to tell which slot to use.
Any settings you do to material "skin" don't stay either. The engine overrides these as well to apply your selected skin tint. That's why there's no glowmaps on bodyparts. You can't make them emit light.
On head meshes though you very well can. But those also have keyword'ed materials and Node names, so I can only assume this is yet another override taking control here.

But to reassure you a little, this has nothing to do with rigging (in which way vertices stick to bones in motion) at all and could never have been "fixed" by re-rigging. It's a texture setting in the NIF.

So you can't make a head mesh use environment mapping, highlight effects and such? That's interesting to know.

Nope, tried Apply_Highlight on a head mesh and it was still a regular looking head texture, no shine. Works on any armor & body meshes, but not on head mesh (or it doesn't take effect). :shrug: