Yes, I used the VFX1 API to get TrackIR working, so should be relatively trivial to use VR headset tracking instead...although only 3DOF, so no sticking your head out of the cockpit as you can in DCS.
Then it's 'just' a case of diverting the video to the headset. That requires some pretty heavy modification of Dosbox and when I've scratched the surface of that, I came to realize how complicated Dosbox is...and the extent of fragmentation of the VR space.
It's definitely something I want to look at again though.