They already have this. A couple of examples include retainers out on the field. Yes, believe it or not, you can run into retainers randomly out in the world, but it's a random event and only happens rarely. I've been playing for years and only recently discovered this - in Coerthas, I ran into a retainer with a pickaxe on his back (I believe it was) and he was mumbling something to himself if you approached him. Forgot what, but I was SO shocked that I looked it up and found out that others had seen this kind of thing as well in other locations. Wow!

Another example is the ghost of Edda. You can find her in Gridania sometimes for a very short time. I've never personally seen this myself, but there have been many accounts of it and a lot of people have posted screenshots and talked about it. There were even rumors of her holding the severed head of her lover, but that seems untrue as no one has ever found a picture of her doing that. Apparently there is only a 1% chance that she will spawn. Also, I guess there's a ghost in bloodshore that's rare to find as well. Who knows how many others they have that no one has discovered! Especially since most people don't explore the world, what with teleporting being way more convenient.