[Suggestion] Randomized terrain? How about randomized mobs?

Here's the idea: In addition to our beloved regular mobs, create one new mob entity with 4 or 5 interchangeable bodyparts/traits that are selected according to the seed, each possibly bestowing positive/negative effects (higher health, fast/slow movement, weakness to fire/water, etc).

It would work kind of like this: as the map is first being generated, this hypothetical mob is assigned (from a list of five or six choices each, and after deciding to walk upright or on all fours) a head, torso, arms and legs, with perhaps a fifth hidden trait deciding vulnerabilities. Now for any given world, one will encounter a (relatively) unique mob that might spit fireballs, have a strong knockback attack, be incredibly difficult to kill without taking advantage of an elemental weakness, the possibilities are endless.

It would add a new dimension of strategy to one's minecraft singleplayer experience by introducing a true wildcard into the fray. It would require a lot of forethought with balancing the possible traits so they aren't too overpowered, but the potion and enchantment systems give me faith that Mojang could pull it off quite well. What do you think, Reddit?