I kind of like the idea, but I'd love it if you weren't limited to being a "criminal". There is, for example, a lot of grey area in being a vigilante.It would be awesome if I could design a costume, wander the streets a night, bring my own special brand of justice. You could set of little hideouts all over town, like converted warehouses, where you could store equipment, extra costumes,
torture chambers interrogation rooms, etc.
TL;DR - Batman simulator.
On another note, a game like this is practically screaming for a classless advancement system. You can use "classes" (or "archetypes", or whatever), but if you set them as starting packages (which grant you starting skills and distribute attributes), then we could be whoever we want (and whatever we're forced to become depending on in-game interactions).
Addiction would be a good thing to model in this game. You could even have it apply to things that aren't drugs. For example, if I mutilate the bodies of a couple victims (take a pinky or ear as a souvenir, for example), then maybe the next time I leave a corpse behind that I don't do that to I take a temporary stat hit, which gets increasingly worse until I do. Or if I go a long time without doing the behavior. Cannibalism would fall under that too. In fact, behavioral addiction would be a good way for someone that had a different archetype to end up becoming a Serial Killer. And if you have the Serial Killer Archetype, you would start with a behavioral addiction.
For inspiration, I second Liberal Crime Squad (I love its Skill system), and also suggest Demon's Souls.
Maybe just make it a skill-based thing? You get such and such points and you allocate them to like
--Deviant Dexterity
Surreptitiousness
Sleight of Hand
Avoidance
--Deceit and Deception
Chicanery
Disguisery
--Aggressive Actions
Fisticuffs
Blunderbussery
Pistoliering
Swashbuckling
Machine Rifles
Repeater Rifles
^Yeah, a skill system like that, where using the skill gives you small upgrades over time, or you can pay to train them. (Though that could tie into the Heat system. If someone was obviously killed by an expert knife fighter, and you have a history of knife training, TA-DA! You're a potential suspect!!
)
Behavioral and Chemical addictions could have their own status screen, where they would appear when you get them, and have levels of their own. The more you feed the addiction, the more XP it gets, and the harder it is to feed, while the penalties for failing to feed them become worse. You lose XP on the addiction once you begin feeling the penalty, and the XP loss is greater the lower your addiction level. Ergo, the less addicted you are, the easier it is to quit.
As for the penalties, Chemical Addictions (such as Alcohol and other drugs, and maybe even Adrenaline (combat high from commiting muder)) would give you Stat penalties, and maybe HP loss (Temporary Max HP, Permanent Max HP, or current HP loss over time, depending on what you're addicted to and how bad it's fucking you up.). Behavioral Addictions could cause you to Pass Out, Increase Appetite (if we're implementing a Satiation system), make you occasionally go Berserk, or have Hallucinatory effects (the screen becomes full of enemies (disguised NPC's) that you think are trying to attack you).
Okay, I think that's enough. I'm not trying to turn this into an Addiction Rougelike, just had an idea that I liked and am running with it. I think it would make for a nice feature though.