They should just create a new gathering class for monsters. Like zooligist or biologist. Or something. Can use shears and taxidermy knife as its tools. Then just spawn corpses to gather from in the level appropriate area. (or happy little monster that don't need to be killed for their wool/feathers/eggs). And if they want to limit the influx of items just make longer respawn of the critters. Then also add a chance for all uncommon trade items to drop from monsters, so you can either kill for random drops or harvest specific ones.