Badger Bill Baldwin is of course still in.
Law enforcement is probably best kept as NPCs players will have to deal with, maybe have a stat for how notorious you are? The higher it gets, the more expensive it is to buy your way out of trouble and the more likely federal agents will come after you.
I was talking about this with someone (I forget, maybe Bialaska) who suggested each character could specialize in one category of crime:
Vice: prostitution, gambling, speakeasies, anything illegal and fun
Violent: Extortion, robbery, hijacking, murder
White collar: money laundering, bribery, fraud, embezzlement
Different specialties encourage players to work together. I.e. to run a successful liquor business you'll need vice to run the speakeasy, white collar to clean the money and buy off the cops, and violent to protect your property or hijack the other guys supply. Anyone can attempt any kind but odds of success are better in your specialty.
Map wise, what about adding a great lake on the north edge? That would open up the prospect of smuggling from Canada.
And anyone who hasn't should check out the Ken Burns documentary Prohibition. Good source of ideas.