Go into Elite Odyssey, as it is right now. Land somewhere and disembark. Open the vanity camera and go to one of the 'shoulder' presets. Activate commander controls. Close the camera UI. You've just activated an already existing basic third-person VR on-foot mode in Odyssey. There's even a glitch where if you activate the vanity cam and headlook at the same time, it becomes a first-person full VR mode. It's slightly glitchy, the UI doesn't work, and interacting with terminals/NPCs doesn't work, but that's basically because you're using the vanity cam, so that is easily fixable by Fdev, if they actually want to do it.
Locomotion is only a small problem, unless, for some reason, you think a 'teleport' mode is actually required in all VR games, without exception. It isn't. Some people are more sensitive to VR-induced motion sickness due to the mismatch between what your eyes are reporting and what your body is feeling. However, there's several solutions to this, only one of which includes introducing a teleport mechanism. For example, one reason why flying games are much less prone to this is because the cockpit gives a static reference which reduces this mismatch. What if Fdev quickly put in an optional helmet overlay to give a similar reference when on-foot?
The UI isn't really a problem at all. All you really need to do is have proper headtracking for the HMD activated on-foot, in exactly the same way that it is in all other parts of the game, and use the current UI. Having proper support for motion controls along the lines of NMS would be nice, but is not necessary.
As for balance, you're going to have to explain that one - as far as I can see, any imbalance caused by VR is minimal, at best.
Frankly, the work needed to get a basic, but functional level of VR into the on-foot parts of Odyssey does not seem to be all that much - it's just that Frontier have gone from having an entire subpage of the elite dangerous site dedicated to extolling how it was 'built for VR' (which is now deleted) to not wanting to give any time to VR development at all.