As far as I understand project developers the intention is to stay with MW nif format (4.0.0.2) and to use original and custom game recourses.
MW heads are animated with morphs. Morphs are not compatible in MW with skin/bones and that is also not recommended in NetImmerse documentation, original MW Max exporter does not support simultaneously physiqued and morphed meshes. Therefore MW heads are stored in separate nifs and attached to bodies by the game engine. Moreover, MW heads animations control is hardcoded: rotation in the direction of nearest NPC/PC or creature; mouth opens depending on the sound volume (say function); eyes blink, I guess, randomly?
In other Gamebryo games (Requiem, Zera) I have seen very nice and doable heads animated with bones. However, more "realistic" facial animations can be achieved with morphs (MW heads have only two morph targets).
Of cause it would be great to remove MW harsh limitations on bone number and names (at least for bodies/clothes/armor/hair), but I think that that it would be more practicable to stay with morphs for heads, may be to add a couple of optional targets like "happy", "sad", "angry"?.that can be controlled via scripts or dialogue options.
Let us wait and see how they are going to realize related to the discussed problem animation control system (including animation scripting functions), dialogues, sound, etc.
You can have different body shapes (races) at present (I have made "advanced" females, two-head giants, winged beast skeleton race, etc.) but they are not always compatible with existing standard clothes/armor meshes (clipping). Similar situation can be observed in Oblivion. This idea was rejected on BB Forum several times.
BTW, I have never seen adjustable PC bodies in Gamebryo based games (there many of them, e.g. several Korean MMORPGs).