This really needs to be done. The combat has barely changed from game to game. Even the shift from character to player based combat hardly affected the strategy used when dealing with a foe. You still have enemies running straight at you, you circle an enemy, dodge back and forth while you make strikes, in the end, it's just whacking something repeatedly until it keels over.
Limb damage would add some much needed tactics to the combat system. It doesn't even need to be a damage-based system. I get that some people think that any sort of locational damage system makes things "too FPS-y" (which is silly, but whatevs guys). Head shots could result in extended stuns, arm hits could reduce attack damage or disarm the opponent, leg shots could cause them to stumble and slow their movement speed. None of these attacks need any change to how much actual
damage is dealt, but they still offer tactical choices on how to bring down an enemy.
Melee power attacks could be redesigned along the lines of attacking certain body zones. Hit down while power attacking to sweep towards the legs, hit right or left to slash at the arm, forward to chop towards the head. There are definitely ways of accomplishing this without requiring the player to aim specifically at any given body part, and without resorting to slow-time abilities.
Finally, enemies need to be built around the idea that locational damage matters. You can't simply introduce half the equation and expect that to fix all of the combat system's woes. This means individual armor values for each limb, it means tower shields to better protect the lower body, it means certain monsters might have tougher skin or thicker skulls requiring the player to fight intelligently. The AI needs to be retooled. If you're lobbing arrows, enemies shouldn't just run straight at you. They should recognize cover opportunities, run serpentine style, switch to their own means of ranged attacks. AI characters that move and react in believable and understandable ways are necessary for any combat system to be effective.
I see it quite difficult to sustain a limb damage system without some sort of vats type ability...
First person shooters accomplish locational damage systems just fine without the presence of a stop/slow time ability. I'm not sure why It'd be any different for TES.