Of endless trouble to GM's is equipping certain NPCs with the gear they should have on them. We solved the problem with Mementos by making them not drop their gear when they die.
This however, is not possible with normal NPCs. So, to help stimulate the economy, and keep NPCs equipped with their favorite items, we've devised a solution.
Some NPCs will now respond to something along the lines of 'hey do you need anything'.
The NPC will pick one of the things it needs and tell you. If you bring it back before someone else does, they will pay you (most of the time).
So if a Sinner is killed and loses all their gear, and you go up to them, they may ask for a cricket bat, or a peice of nexus clothing.
They don't buy something they are looking for, when they already have it on them.
They don't just buy weapons and armor though, we have the ability to configure any NPC to look for specific things and keep looking until they get it.
So some NPCs are setup to want tools of their trade (For instance, a mechanic will always want a mechanics toolbelt, if they don't have one).
A lot of NPCs are also setup to want drugs. This is the major economic stimulus. The NPC will ask for a drug and when you give it to them, they will have it, and wont want it anymore. But, over a few days, they will -use- the drug, and when its gone, they'll be wanting more again.