Considering AVP2 support 3D (stereoscopic camera), what should be coded is the camera system to get motion capture from the helmet.
I doubt it requires Lithtech engine to do so, the source code could simply do it.
But then the code is so old and so badly documented and rare are the people who ever touched it or who possess it.
It's supposed illegal, you won't find it anywhere and even if you manage in the dark web to retrieve it, the doc is so unexistent that it may take years to do it unlike Half Life which has a huge fan base and which code has been studied for decade and not a single line is unknown to any modder.
Another thing to take account is the game was not made with VR in mind.
You don't even see the characters leg and the field of view of each character match perfectly the limit of every model / mesh.
Add wider field of view or the possibility to turn the head and it just looks terrible like this:
There's very little margin to move the viewer from the axe without revealing that the weapon / hands only exist partially.
It would require an entire new mesh / rig system
And AVP2 wasn't made for a smooth workflow with 3D app of nowadays in mind. There are only a few versions of Maya, 3DS and lightwave with which the import/export system work and redoing all the anims would be a pain in the ass even for a trained animator.