I don't see how you can say that when i pointed out situations in the OP and people have been suggesting uses of it this whole topic.
impossible??? whats impossible???
It's impossible because the game is packed full of skinny cooridors and many, many places where your body will clip through walls. If you go prone the game will need to auto-sheath your blade/axe and re-draw it when you get up (that'd be quite annoying and tacked-on)
Not to mention nobody with half a brain would ever find a practical application for laying down whens there's monsters and blade wielding guards around. Enemies will need a new set of animations for striking you while you are on the ground otherwise it'll look like they are swiping at the air, not to mention if you were prone any guard with half a brain would simply plunge his blade into your spine, seems awfully risky. Long story short no moron would use it in real life, and the one possible use for it is ambiguous at best. When do you ever find yourself in the situation where you are overlooking an enemy camp? never, you never do. Are you just going to arbitrarily go prone every time you see any enemy? For role playing value maybe? "Look at me, I'm a role-playing a person who's about to get stabbed in the back while I'm crawling and shuffling around the floor!"
There's simply not a single situation you'd ever encounter in the game where prone is more suitable than the basic crouch/sneak. It's a LOT of extra work for little to no use. It's prone for prone's sake, it's not going to be useful in the slightest.