If a musician is totally deaf, they should be able to hear themselves play from the bone conduction in their head.
This is incorrect. If they have sensorineural hearing loss (the most likely problem for musicians), bone conduction isn't going to help: it will bring the vibration to the cochlea where it is not going to be picked up. Bone conduction only helps with conductive losses (such as when you suffer from "pure" otosclerosis).