Spirit Mob (addition to Nether)

We all kill mobs in Minecraft. It is sad, but we must admit that we do. What I propose is a way to make every player feel better with themselves by making use of a clever new addition to the game. This mob would be a neutral simple "typical ghost" figure mob that roams around the Nether.

My idea consists of two things:

1-Killing mobs

2-Mobs be teleported to the Nether

So let's say that in the early game you manage to make a really good cow farm, and so you kill thousands of cow till your first enter the Nether, that would mean that 99% of all the Spirit would make cow sounds. But then you decide you also need some bonemeal and gunpowder so you make a general mob grinder and you start killing lots of creepers and skeletons. When you come to the Nether again the Spirit would be making 45% cow sounds, 30% skeleton sounds, 10% creeper sounds and so on and so forth. This would work because it involves only creating a new mob to roam the Nether, using already available sounds to create a deeper feeling inside of the Nether, and the Player kill statistics to define what are the odds of a particular sound playing next.