Weeping Angel from Doctor Who
I thinking about this:
The killer is moving around, but in the map there are some "stone angels" too and you can teleport to them like the unknown. The angels just there and moving closely to the nearest survivor like nemesis zombies but only when you not watching them. So it's a nemesis zombie, unknown teleportation, ghost face reveal mechanic combined and they do killer instinct or make survivors scream when close enough.
About the perks: i don't care, just want to play with the character. I leave this part to the devs :)
Last thing: maybe a dark power like the dredge one, but not for the hole map, just for the chase or creating small area dark zones for a short period of time.
I think the licence is not cheap and some of the fans doesn't even know what is Doctor Who but if not in this shape, i really want to see this character in the future of the dbd killers list. :)