If I understand your request correctly, that is already possible.
1. Go to the Input page of the vorpX ingame menu
2. Make sure that “Override X-Box Gamepad” is set to “Off”
3. Set “Head Tracking As Gamepad” to “On”
After doing so a few additional settings appear in the menu. How these have to be set depends on the game.
Caveat: games heavily filter and process gamepad input, so this method is rather laggy and far from ideal, only use it as a last resort. If your game happens to support TrackIR (many racing/flight sims do), check OpenTrack instead, which can translate head tracking to TrackIR input.