This would be something I'd like to see, something with a lot more bite. An extra couple of difficulty increases would add so much and It would be like playing a brand new game.
Have you tried turning off the HUD? That one simple move increases the difficulty in a number of ways. Combat wise, by removing the "red dots", no HUD play forces you to look around for enemies and listen to sounds to determine where they might be. No crosshair makes aiming spells and arrows more challenging. No sneak crosshair means you really have to pay attention to sights and sounds in the game to determine whether you are being detected. Plus, no compass makes navigating the open world more interesting.
The whole no health/magicka/stamina bar is a bit of a pain and its stupid we cannot turn off the rest but keep these, but if its challenge you are after, having no health bar does increase the challenge of the game.
Now I agree that Bethesda bungled the options menu by having way too few options for how to fine tune the game with numeroud difficulty sliders that affected things like monster spawn level, sneak difficulty, hardcoe mode like FNV, etc., but at least they did give the option to turn off HUD. You should try it, if you haven't already.