There will be a flare in the center of the map and as you get farther away from the flare it gets darker. The flash of firing guns and grenades will still light up a small local area. Gun fire will be dependent on the gun maybe, larger gun larger light radius, but it should never be more than 10-15 feet from the player. Explosives would be a slightly large radius. The max area you can see when you are in the dark will be about 5 feet. Or 2 meters for my EU peps. It could be played as a Free for All or a team based game I suppose. Or you could even have it where the objective would be to restart/fix a generator so the power will come back on.
The map specific to this will be a large enclosed rectangle, probably a gym. It will have lots of low level obstacles to SMART over, a few mediums, and maybe a large/ tall place that is hollow, where two players are like "Oh crap!" and have to react quickly to each other. And it would probably strictly be a FFA arena or a smaller team based map.
I realize that this might have problems with the medic and engineer.
The medic needs to get to people to heal them so maybe a read icon with the medic cross on it pops up? Maybe seen through cover? OR maybe we keep it really hard and they have to use their ears? Or something else? Also the medics health packs have been spiked with a night vision drug/ a new syringe altogether. It provides limited night vision to about 10-15 feet (3- 4.5 meters EU) that wears off in about 30 seconds. Medic has limited supply of course.
Engineer's turret can only see into areas with light maybe, or that they have a much smaller range. (10 feet? Or 3 meters for EU?) Maybe EMP knocked out the lights and it affected the turrets targeting too? And the turret would probably let off a glowing "sheet" of light from its targeting beam. Also maybe the engi could attach the turret to a power cable that would increase the range by 10-15 feet, but at the cost of the turret taking damage to the internal wiring of the turret. (5-10 hp a second) The Engi will be able to repair lights/ generator maybe? His mines will also have the secondary effect of a blast of light (phosphorus) that would cause spots on the vision of night vision wearers or a 3 to 5 second blindness.
The Operative. I think we could give him a small flare with limit ammo of course. They would stay alight for 10-15 seconds. And maybe limited night vision goggles. They would last around 5-10 seconds and would be more for locating an enemy to kill then moving in the dark toward they enemy. They would have a 20-30 second recharge time, and there range would be quite far if not infinite. He will get splotchy vision if bright lights flash inside 10 feet. Gun fire flashes would cause a heavy haze on that section of the screen for 5 seconds, and explosions cause even more visual damage with a black circle on your vision where your retina fried. This will last for 15 seconds.
The soldier I can only think of a few things. The soldier will be able to give out tracer rounds. When you fire your gun with tracer rounds where ever the bullet goes it lights up, in a sphere around the bullet, a "corridor" of soft light. IT will not effect night scopes. It will reach out about 5-10 feet. Useful for showing up your enemy a little. It wont be very bright, a little lighter than a dim light bulb. You wouldn't get too many of them maybe 10 rounds. But they would be dispersed with your regular ammo, every fifth round being a tracer. Or it could be used as a secondary ability by the player, with a alt fire button launching a tracer. I think the soldier would be able to carry 3 tracer mags maybe 4. I'm not sure if the tracers would cause extra damage. I they do it wouldn't be too much. Maybe 5 extra damage?
The purpose of this mod/DLC is to add an extra layer on the game, the interaction with light. All the values I have spoken of are completely variable, and there are many options. Maybe the lights come in in 10 second intervals. Maybe instead of a Central Flare it will be a light hanging from the ceiling, a hole letting in a ray of sun that lights up a whole stretch of the level.
Your comments are all appreciated.