Personally, I think to make things more interesting/realistic, the money laundering should go through registered businesses. A criminal organization is not a business, necessarily, unless they own a legitimate business. Gangs/criminal enterprises would have to work with business partners to setup "fronts" for them to launder their money. This would also open up possibilities for new police units to enforce laws pertaining to fraud/money laundering.
Money laundering, or the use of "dirty money" on its own is a played out/no-rp value element of a lot of communities, so adding it in a similar fashion where everyone has to go through some criminal enterprise is just predictable.