I have always been disappointed with how under-used the light system has been in all of Seatribe's titles. Custom clients quickly remove daylight and weather effects and torches/light sources basically become dead content.
I would like to see some sort of buff added that would be based on the current amount of light near your character. Why can I perfectly craft a detailed ring in a dark mine shaft? How can I mine the most ore possible from a cave tile if I am in complete darkness?
On top of your attribute/tool cap, I would like to see a small boost added as well based on lighting in your area. Say your attributes cap out a ring at quality 85, a well-lit room should buff that cap up to 90.
Assume you are in a mine that has no light at all, you mine a tile and get 4 pieces of ore out of it. Now assume that you were wearing a lit miner's helmet when you mined that tile. Because of your ability to see the ore in the wall, you got 6-7 pieces instead of 4.
I'm sure there are other instances where lighting could play a part, but these are just some general examples.