Traditionally, non-unique game mobs and NPCs are of the cookie-cutter type. Seen one, seen 'em all, and you instantly know their behavior, stats and strong/weak points. Games however become ever more immersive, and this seems like one of the last hurdles to take in that regard.
A quick search for this shows mods like SetBody for Oblivion which allegedly gives all NPCs random bodies (lore friendly), and I've found some DnD discussions about random character creation tools for DMs, but this is only putting a random look on a predefined character. With full randomization I mean not only random looks (to an extend of course - no orc looks on elves of course), but also random abilities, random AI level, etc. I'd even go as far as e.g. random attack style (weapon choice, etc.) and AI.
On the one hand this would make games far more interesting, but on the other hand it might make them a lot harder to play. Imagine a horde shooter which traditionally would e.g. have 10 basic enemy types, each with their own unique looks, stats and attack style. In the new set-up, you wouldn't be able to know how they would react to you upfront, nor would you be able to know how to best handle them. Basically every enemy you encounter would be fresh, and you cannot rely on things anymore like "Oh, that zombie is red - it's an exploding one" or "it's obviously one of the 10 available elf body types - it'll surely attack with this-and-that spell when I get closer than this-or-that distance". It seems like it could only ever work in more strategic games where you have time to study and handle each NPC and mob individually.
Regardless of whether current gaming platforms are up to it hardware wise, would players actually like and want it due to the above? Or would it only appeal to a niche of the player base, and is it thus not more common today? And I think current hardware is up to the task; if not, then it's easy to spend say 30 seconds upfront to pre-render the mobs upfront before a level starts, and just create a strong AI with diverse parameters that can be randomly tweaked per mob to weaken its abilities in a random way (a bit weaker path finding skills, smaller alert distance, etc.).
If anyone has any example of such games: please share; I'd be nice to try it on for size :)