Believe me - it is possible, you just need ‘origin points’ and memory muscle 
at first it is not easy, but quickly works very good - exactly as using keyboard without watching it when you type. I added one origin point in middle and then things with buttons go very easy.
You see green knobs? these are most used ones - outer-inner left, outer-inner right for gns430/530, these I 3d printed, and they are different diameter and height - extremely easy to differ. rest four I probably will also 3d print with different shapes (probably based on some AP/nav knobs, idk yet) but so far I don’t have much trouble with them
That is something I cannot argue, but didn’t think about, because all that glass cockpits are soooo boring for me 
I love steam-gauges planes and spend most time in: DC-6, Piper Arrow, P-38L.
Of course it is not possible to map A320, and for modern airliners controllers/mouse is needed (however typing in anything on FMC in A320 looks the same way bad with vr controller and mouse - there would need keyboard/FMC simulator unit).
Well depends - I can map all switches of DC-6, it is possible, takes time, but it can be done. If it is possible to remember them? yeah, most for sure (and yes I can remember them). But for me in case of this plane, quite a few buttons are used once - going from “cold and dark” to “ready to fly”, and then on shutdown. There I simply use mouse, since it is impossible to map f###### button on checklist window to mark entry as checked and going with interactive checklist is so much fun.
I know, as I said - even tough I don’t need it, I understand that people want that. I might not agree that it will be better than buttons and knobs / will be as some people imagine or might not agree that it should be priority now, but I’m not gonna deny that people want that. I’m not angry - it is good that developers (at least to some degree) listen to community I would prefer devs to focus purely on performance and image quality (and few other bugs related do VR), since that is touching everyone.
But I also know that it might be different teams working on that, or some changes require more internal testing or iterations - I know software development process in complex systems, I do that every day in work
So if I sound bit salty, then sorry, I just wanted to present other point of view, since this topic is focused on discussion and reasoning around VR controllers.
One think round that would be game changer - would be hand tracking, but we are not there yet, current iteration of that interfaces is neither popular, nor precise (or often loose tracking). So maybe next gen HMDs, maybe one generation more from next gen we will get something nice in that matter. Maybe some good, popular haptic gloves? Who knows, but it seems that it should go that way at some point