I think the ability to rob banks for money as a gangster would be amazing. And getting paid to catch those who steal as a cop would make it a great cops vs gangsters idea to really bring out the theme. Rob bank fighting off npc cops, then once you're out you need to run to a safe location while marked on the map with a $500 bounty. Robbing a bank would be difficult though, would need several people. And if you get caught you can't rob again for a week.