Make it so only criminal faction top ranks can sell, not just people with rank over 70+. Perhaps return some sort of ARUN-like group to whom group leaders apply for BM access.
It's fine the way it is, but maybe work onto the Cartel system and allow groups to enter the drugmarket. For example the Pavano Crime Family wants to buy 3kg of meth for a cheap price, they access the black market /setoffer meth[or any other drug] [p/g price] and later pick it up once that amount is sold to. Also what happened to the relation system that was mentioned before with the said Cartel? I believe there was something said about having good relations and getting better prices for working strictly with one Cartel.