This is a fairly complex suggestion, in that it would greatly change certain aspects of the game, and require the addition of new abilities/items.
Lighting should be similar to that of Minecraft: surface blocks (and players standing on them) are fully lit, and all blocks project shadows directly below them, their intensity based on the lighting of surrounding blocks.
What would have to be added:
- Flashlights. While giving your vision of the area, flashlights would also have the disadvantage of making you more visible to your enemies.
- Torches/static lights. For more advanced defenses.
The addition of lighting would make tunnelling and tunnel navigation harder.
There would be more purpose to hiding in buildings/under trees.
A new type of structure would see some play: a large roofed room, which a defender can camp and have the surprise advantage against attackers.