[JustADude]

Okay, so this is a simple one... would a Possession spirit possessing a person with Paraplegia or Quadriplegia be able to use the relevant limbs, or would the Spirit be just as SoL as the host?

Also, how would Channeling affect the situation, if at all?

[RiggerBob]

It's stated for unanimated vessels that the spirit can perform actions that the vessel could mechanically perform. So it should also be able to move all body parts even if the possessed person normally can't do this, because of lacking the nervous connection.