I would love to see a orginzation of crime in the city, so instead of it being 1 or 2 people killing someone you could actually trace it back to a mafia/gang and if you are smart enough take the whole gang down, I would love to see this and also corrupt cops (meaning you can bribe them to let you search a crime scene for a set duration)
also I think a really nice feature would be the ability to plant evidence, say you have a killer but you can place them at the scene of crime (you missed the camera window) then you know they killed a dude with a gun you could plant said gun on them when you arrest them