I'm wondering if there would be problems getting the spine to line up properly with a separated neck.
But, I do see in NIFScope that the spine part is separate from the ribcage. Perhaps a good approach for a modeler would be to remove the spine from the torso entirely (it's Shannon's work in MCA), and work from there to make a spine and neck that match up well.
I would also be very interested in the parts for this if it is done, for some mods I am working on.