Something that I think would be cool with later updates is a system to allow killers to get smarter the longer they are loose. Possibly even recognizing the player is after them, and taunting or harassing you. Maybe even going into hiding if you get too close. Making a cold case and letting other killers become active.
A very rough idea to have the Holms and Moriarty type cases. But I feel like some sort of killer evolution would be cool.