Love this idea!!! Perhaps add it so you can buy those empty "store" building in towns and such also.. Those could be owned by players and limited to the types of vendors and storage ability. Where the large atm building are gang only. Add access ability to different storage so if your offering to buy certain mats but one want 1 and 2s to be able to access it, but Raw mats can be accessed by any gang member ...
Gangs could actual have a base of operations
Maybe make it so you can have a type of business such as a brewery were civs could produce and see cheaper liquor "add wine and beer etc" and it be legal
ideas are endless
+1000