fair
programmer considered some form of anchor point IK that matches each head?
i couldn't begin to type how that works in code, though..
when i animate certain actions or full animations involving 2 characters, i can usually copy the entire animation set of a character's bone positions, to paste the animation set onto another model/character -
if any adjustments need to be made, sometimes only the
groove bone needs to be repositioned, then everything else works without needing extensive adjustments.
though this is very relative ^
i can picture a good oral animation that works with one of the heads, also working with all of them, if something similar to a
groove bone can be adjusted?
anything that leg related IKs are parented to, can usually reposition a model in such a way that it skips the need for reanimating an animation for every in-game head.
it may also just need a neck bone separate from the head bone, so only a neck adjustment value would need to be tweaked, to allow for every head to work.