They need to make it a mmorpg.
You wouldn't be able to distinguish a human player from a computer player. It'd be a huge city, enough for a server of people. You could go in and out of buildings. Get money and become powerful, hire goons to kill people for you and countrol the city. It would be one small, big city. If that makes sense. You could be a cop, you could get any random job. It'd be like grand theft sims. That's why online play would be fun. If you got killed, your character would end up in a hospital. If you have medicare. You could go to jail, and you could bust your friends out. You could work together with your friends to rob a bank, and evade the cops.
And your character could become a junkie.
I have alot of ideas, but this is just my delerious rambling
Most people would say it'd be too chaotic, it wouldn't be choatic at all. Everyoen would start with nothing, and the towns citizens are very anti-crime. So if you run up to some random person and punch her, the towns good samaritans would kick your ass. So you have to be careful, get a job. It wouldn't be hard to make money, but just hard enough so if you wanted weapons, it'd take some time. Eventually, yeah, it would just be one big street war going on all the time. But that'd be cool, because the city would adapt. Stores would get tighter security, or at a higher spectrum tanks would start patrolling the streets. You'd have to eat. And sleep. You'd need an ingame apartment, if you slept on the street like a hobo you'd get mugged. You could rob peoples houses.
People could be pushers, like in dope wars. And drugs would have in-game effects, so people would waste thier in-game money on them. Youcould become a junkie! Fun!
There'd be charts, like in infantry. Listing the people with top 100 kills, cash, ect.