Well there you go then, I was about to dive in to investigate this, thanks mate I would have wasted so much time. What you've done does look absolutely grand though, though the head does look suspiciously like it's from another game :frog:
I'm not sure because it's been a while but there is a specific bone for the face and the hair, right? I physiqued a hair so there must be one I guess. If that is the case, then why not weigh the bottom of the neck entirely on the neck bone or whatever bone the neck is using by default and then as you go up making vertices more and more dependent of the movements of the head bone until at the top, at the line between the neck and head, the vertices are weighed to follow the head bone and only that. If the head and neck meshes are modeled correctly (ie it's the same mesh just cut at the bottom of the head, a la BB) it could work, couldn't it? And you wouldn't have to physique/skin/rig the head mesh and would get to keep facial animations.
If that makes any sense
edit: Bahamut, if you physique the head and don't see it in the race selection menu at the beginning of the game, try cloning your head mesh, removing all physique/skin data from the clone, renaming it to something else than the name of a bone, then moving it to 0,0,0. The clone should appear in chargen, but only then. It worked for me for my lady pirate hairstyle mod (I find the mesh crappy but you can still download it off pes to see what I mean, just load it up in nifskope)