I used to play 'Tyrant,' a java rogue-like that was very similar to dweller but is no longer in development.
One of my favorite features was that there were apple trees that randomly dropped apples of different types.
So you could run around towns with apple trees collecting apples of different values then sell them to merchants. It was a great gold-grind feature that I would love to see in dweller possibly by adding more types of mushrooms above ground that randomly regenerate with turns.