This would require them to all be NPCs instead of actors. Actors cannot hold weapons or shoot or move etc. while NPCs can. The problem is, NPCs take up a player slot. That means more resources, more lag, longer compilation time, and more potential for things to go wrong. There would need to be over 200 NPCs on the server, just to stand in shops.
I guess one solution could be to only spawn in the NPCs when someone enters the shops, but it can take 5 seconds or more for them to spawn sometimes, and I don't want players seeing NPCs appearing in front of them 5 seconds after they enter a store.... I also would have to work out wtf would happen if the server is full of players as more NPCs wouldn't be able to join...
It's something I'd love to add if it were easier and more viable and worth it. But for now, it's none of those.