The option to add corrective shape keys to vrc seems like a really low hanging fruit that could greatly increase the polish on models.
UI could be something as simple as:
[right elbow]:[insert shapekey here]
[left elbow]:[insert shapekey here]
. . .
. . .
Implementation:
(degrees elbow is bent with)°*(100/(max degrees elbow can bend)°) = incrementation of shapekey
I assume the implementation of this would be extremely simple, but in return greatly help creators interested in polished models.
Regards,