I know the topic of 'how to make light an actual mechanic' has been brought up in the past, and I felt I had a good idea for it.
Would be cool if Light levels affects the area of view a character has. Currently, characters can see an area roughly smaller than 100x100 tiles/one map grid. using this idea, going into a cave would allow you to see 10x10 or even 5x5 tiles around a character.
By "see" i mean objects/entities loaded onto the screen. so you wouldnt be able to see a bat without light until you walked right up to it, which is very dangerous. Likewise, walking around in the woods at night, you wouldn't see the bear 15 tiles in front of you until it was too late.
maybe to prevent tedium, pclaims and vclaims would lessen the affect of darkness so you could work at night without having to spend a lot of time lighting torches.