It should be doable. If you watch something on Virtual Desktop, and stretch the image across your entire field of view, it is still in 2d.
Five years ago, I was flying around in this 2d VR rig.
In 2d, you still perceive depth and range. Even in 2d, this rig would give me butterflies in my stomach.
Native 6dof head tracking would create a pseudo 3d effect.