Later, when BI has developed their new engine for DayZ and there are no more unforeseen delays when it comes to any part of development - whether it's lighting, AI, performance or otherwise; I want Dean Hall and the devs to introduce a set of mechanics that affects the character's actions based on the lighting.

Pretty much, as simple as it sounds, your character wouldn't be able to do certain things - like open cans of food or operate weapons or machinery, while in complete darkness. For this to not be completely black or white(hehe) - your character would still be able to perform most tasks in low light, but with a level of uncertainty as of it's outcome. Like taking longer to put in a magazine, start a car, or if it involves something sharp - entirely missing a vein for an injection.

Aside from that, it would add a whole new layer of tactics into the game - as people would be forced to balance lighting, their survival performance, being seen by zombies, and most importantly - bandits.