Quick suggestion got the idea off the credit card thing when those factions were competing to change their drug racket. Currently criminals have 2 ways to generate income by conventional racket means: Gun selling and Drugs. My suggestion is to implement a 3rd racket addition such as: forged checks, counterfeit credit cards, embezzled union bonds, etc. This would work similarly to drugs except no processing and not as much profit, similar to how oil works. You would place the order for the shipment at a pay phone rather than your typical criminal racket npc. Once you collect the shipment you gotta trade or sell it via rumour to have the other person sell it to an npc on the map (could use existing drug npcs.)
Why add another criminal way of making money?
1. Way more mafia
2. More crimes for police to go after rather than guns, violence, or drugs.
3. More grinding shipments for the don