Which would render it useless... You'd have to go far too in depth with the design of each area and mob to make it usable and frankly it just wouldn't pay off. Lets face it, stealth really isn't that useful aside from scouting as it is and making it more realistic so its more likely to fail would make it even less so.
My point is that stealth should be useless in certain situations or it is lame.
Why would you have to go into depth in each area with the design? I don't see why you can have light based sneaking in Oblivion, but not this game.