> The chief problem is that without eye tracking, it's incredibly UNFUN to use your head for movements that your eyes could otherwise have done for you. Mind you when the HMDs were much heavier back then it sucked a lot more, but it's still pretty shitty not being able to glance aside.

Isn't that more of a problem of field of view? With a wide enough field of view, you could just look at whatever you wanted to. Basically make it like real life, where what you look at is the combination of where your head is pointed, which the computer needs to use to update the screen, and where your eye is looking, which the computer doesn't need to care about. Or are you thinking of using eye tracking to something else, like determining what you're pointing at like a mouse? Yet another option you have in VR is what you're targeting, like how Dactyl Nightmare uses the gun you're holding to map directly into the virtual world's gun. Using the head position to AIM rather than just LOOK seems like a bad way of doing things.