I feel like a cool feature would be able to become vigilantes in the city. I mean, I feel like it would be cool to become one. I have watched Arrow in its entirety and I like a lot of DC stuff such as Batman, Superman, the list goes on, and I really feel like it would be cool to become a vigilante. You could either be friends with the cops or in the cop's radar. I also feel like Vigilantes should be able to arrest citizens and call the cops to that location to pick them up. Tasers, cuffs, and all that stuff would be really good to give to players, not just cops.
I guess Watch Dogs also falls into this category because they are basically vigilantes. If we could hack into techs like CCTV cameras or police radios, that would be really cool for both the bad and the good side. Gangs or organizations could gang up on cops if they are really organized and hacked into their technology. Vigilantes would be good as well if the cops are dealing with one thing, vigilantes could help them out with another. I feel like vigilantes are just a cool way for citizens to help the police without donations or all that, to actually suit up and risk their lives and stuff.