This is an idea I’ve had for a while, and I just remembered it because it might be more useful now due to the fairly recent change with NPCs spawning “rare” guns and attachments. It could also give some purpose to a very overlooked item.
Currently, the Sewer and Barge NPCs are static, they don’t move at all. With the Barge NPC, this is fairly reasonable, as you want to ensure the map has the best chance of being used and explored. However, with my idea, it could expand the exploration aspect a bit further.
My suggestion is to have the Sewer NPC move around every restart. Obviously, he would still have a few regular spots, such as his current location by the fire pit in the sewer. But placing him in a random alleyway somewhere on the map would fit well with how black market dealers should operate. This NPC has been sitting in the same spot for 2 years since I started playing.
This idea is inspired by Perp. Whenever their black market NPC moves, players receive a message on their phone. Why not put the pager to use in a similar way? You could add a notification sound, and the black market NPC would page every player with his location at each restart, repeating every time.
This would help prevent the need for Sewer NPC characters, and, if you feel strongly about it, the same could be applied to the Barge NPC/chars as well.