Technically it doesn't seem impossible that someone might attack criminals without being an official police. Say, if you see a person with a gun taking someone hostage and you go and attack them helping that person, you would be considered a vigilante. There wouldn't need to be directly implemented into the game and since people can make own stores, someone might start designing suits for vigilantes in the future as far from I know there's nothing to prevent it, and yes vigilantes are in risk of ending up in jail themselves as they are breaking the law.
In real life people can literally put on a suit and fight criminals if they want to, even though very few actually do it.