Blackout is already in the game, however it can only be invoked client-sided. I'll make a client-sided add-on and an event to tell the client to do that.
Hold on.http://lh.rs/2fDJE6I3TQTpIf enabled on a server, adds a "setBlackOut" event to clients. Only works on clients who have the event add-on as well. The first argument is a boolean for whether to fade in or out (yes, it stays until you die or get a fade out). The second argument is the amount of MS (1/1000 of a second) the fade should take. Accepts parameters in the range 1 (0.001 seconds) to 10000 (10 seconds).