Looks like a great piece of kit... perfect for sim racing
as far as FPS controls, maybe what would work (after getting used to it) would be using keyboard for forward back, rotate left & right, and strafing, mouse for aiming cross-hair and VR headset for aiming camera relative to body position....
The cross-hair would be positioned by the mouse relative to the direction the body is facing, not the head. You could have a key/button that immediately (with customizable smoothing like 'look' buttons in LFS) aligns the body position and cross-hair with the VR aim, so that you can lock onto things quickly...
I think something along these lines would become intuitive very quickly.