Although I wouldn't hold a weapon in a hand full of rings... must not be the most practical thing...
As for clothes under armor (ah, daggerfall paperdoll awesomeness), I suppose the clipping is a high concern too for today's standards. I actually don't care much about clipping as long as it is not 100% of the time in front of your face... But imagine the work of fitting all armor pieces to match as flawlessly as possible all the piece of cloth ? might be too much work for the benefits, in dev's eyes.
Sorry but I'm a little confused by this "Balance issue is irrelevant IMO it is more related to performance/memory saving for hardware reason" What???
Anyway I personally see no reason why you can't wear at least two rings, one one each hand. Again, Dragon Age allows two rings.
With regards to "Balancing" tweak the game to even it out a little. And speaking of "balance" at level 54 there's nothing in the game I can't handle, and I'm not even using cheats, or have elaborate armor.
Anyway tweak the game to allow us to wear two rings. This isn't so unrealistic in a D&D world.