One of the big problems with motion sickness in VR comes from the player’s movement being different from what the brain expects. There was this multi-directional treadmill device I saw a few years back that moved the user in the opposite direction of where they walked in the XY axis. If I recall correctly it did not allow for vertical movement as the harness is attached to a fixed point around the waist. I think an improvement would be to have the harness attached to the ceiling by 3 or 4 ropes. Then the tension of these ropes can be used to determine the player’s movement in all 3 dimensions (if the player crouches then the ropes will be pulled downwards, etc). All other parts of the setup would remain the same including the treadmill. With this setup the player can probably jump and crouch similar to in real life.