I wish there was a mod like that, but it doesn't go far enough in what I'm talking about.
There's a game called Shadows of Doubt that's based on being a detective, but at a much deeper level where nothing is really scripted and the mysteries you solve are created procedurally, anyway, what I'm getting at by mentioning that game is that that's the level of immersion I'm talking about.
Total freedom to do as you want and act as you see fit, if you see a character on the street you can follow her, stalk her, always being careful not to get caught, find out where she lives, enter her house when she's not there, etc. but with the added bonus that of course, you're human too, you need to eat, pay bills, earn money, all while balancing your "activities" with your life. Maybe you even have to learn to pick locks, get better at stalking, detect security in homes, in general learn and improve your skills.
You might see a character who is marked as "famous" and having cameras in their home might give you content to sell, but they live in a safe place and you can challenge yourself to break into their home. Or you can target low-risk prey in impoverished parts of the city.
And obviously they would create "Dark Mind" mods for the game, we all know each other.