I'm going to propose a system for narcotics, pretty loose to start. More like outlining what feature it could include, or the steps that might be involved in it.
First off, whatever people are comfortable with is what we should do. I'll say that we need drugs, but whether we need every single substance people can put into their bodies, just the key note ones, or just the ones people don't feel icky talking about, is up to the community.
I'm basically ok with everything. We don't need to get too deep into the difference between these drugs, even if ingested, as long as they stand apart for the player in terms of value, difficulty and inherent risk. More below. Skills and attributes are just listed so people can get a sense of what might apply.
So, drugs. Three parts.
Supply.
Processing.
Selling.
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Supply. Whether you grow it, buy it "wholesale", steal it or make it out of some other product, it has to come from somewhere. The question becomes is the player a middle man, just pushing processed product, or are they doing the whole shebang from step 1 to step 10? There's a gameplay element here. Starting your own drug business would require more investment from the player, but turn a higher profit. Being a middle man would turn quicker but lower profit, and require a lot less logistics on the player's part. However you do it, it also include deals going bad, or, if the player is growing/brewing their own supply, they might become a target for law enforcement or OTHER criminals.
Next to each entry is listed the potential yield for each source.
Sources:
Other dealers (purchase/rob or kill) (HIGH)
Grow it. (HIGH)
Purchase/steal the necessary legal ingredients. (HIGH)
Steal it from the authorities, rob or kill them. (MED)
Steal/rob/kill drug users. (LOW)
Associated Skills/Attributes:
Charisma
Street smarts
Negotiating
Intimidation
Bluff
Business
Processing. Most drugs have to be processed in some way for consumption, even if it just means breaking it up into smaller quantities to sell to people at a higher price. Again the question for the player becomes, how involved in the process do they want to get? Let's assume that when players acquire a significant amount of any substance, whether they bought it or stole it, it has a required processing time relative to the quantity and substance type.
But not only is it a turn over time, it's a coefficient, that determines how much of raw product you turn into finished product. Your skills should adjust how well you turn 30kg of X into substance Y, or how many grams your plants yield. The conversion rate could be different if you're already working with finished product, then you'd only lose a little bit as stuff gets spilled on the floor. (Or perhaps you start dipping into your own product if you've got an addiction.)
So, processing should involve:
-Time. Lots of time eventually for lots of product.
-Land. You can't grow/brew/bag drugs without a place to do it in private.
-Equipment. All drugs require some equipment to make. Even if it's just a garden hose, a trowel or plastic baggies. We could abstract this to a general upkeep cost, or a one time set up cost via the items people buy/beg/steal to bring together.
-Skill. Skill reduces overall processing time and increases yield. (The yield should never be greater than a 1:1 ratio however.)
Associated Skills/Attributes:
Intelligence
Farming
Chemistry
Cooking?
Selling. I see this sort of as a general text option you could have with all NPCs. "Hey do you wanna buy some drugs?" or "Hey do you wanna buy...." and then you pick what you have on you from a displayed list, and the NPC reacts based either on their preference for a certain kind of drug, or their overall opinion of drugs. Selling in front of "the man" would check against some relevant skill to see if you can keep it concealed, or they're on to you and do their thing. But there should also be a tie-in to your general heat rating, because the more people you deal to, the more word spreads that you're "the guy" and that eventually makes its way back to "the man."
Associated Skills/Attributes:
Perception
Charisma
Street smarts
Sleight of hand
Business
Negotiation
The List of Substances
Just so we know what's on the table.
Listed next to each entry is is the drug's relative value, it's relative cost of investment and processing time, it's availability and it's level of criminality. An * means I personally think it's shouldn't be growable, because I think growing coca plants in people's backyards kind of stretches the simulation a little far. Meth labs, however, are entirely feasible.
Marijuana (LOW, LOW, HIGH, LOW)
Cocaine* (MED, MED, LOW, HIGH)
Crack (MED, LOW, MED, HIGH)
Methamphetamines (HIGH, HIGH, HIGH, HIGH)
Heroin (HIGH, HIGH, LOW, HIGH)
Opium* (HIGH, HIGH, MED, HIGH)
LSD (LOW, MED, LOW, HIGH)
Mushrooms (MED, MED, MED, LOW)
Ecstasy (MED, MED, MED, HIGH)
Prescription Medicines (MED, LOW, MED, MED)
A note on criminality: It should not only affect how harshly law enforcement sees it (how much heat it generates, ect...) but also how likely it is that drug deals of ANY kind go wrong. You're dealing with other criminals, after all, and the higher up the drug schedule you go, the more dangerous and untrustworthy those people become.
That's all I got for the moment.