I'll post some later tonight when not swamped at work crunch time, what would end this is legalizing most of the black market since all you need to make a million dollars right now is a handful of drug delivery drivers and a couple of guns to shoot at and rob all the other drivers. Cities can then break up the entrenched corruption since they don't need a "boss crew" to keep order. Prisons won't be overcrowded with drug convictions either.

There will always be gangs but they won't have access to millions in capital to fund huge street wars thus less incentive for new recruits to join them.

It's the plot to Sons of Anarchy.