Dumping the air from the lights is not a good idea. The heat will just build by the hour. Then your trying to cool the lights with hotter air. pull air from the eve, and exhaust out. push the heat from the lights out of the attic. you could exhaust in the eve, if sealed lights, with no odor. What is the average temp up there? Better if you chart it by the hour, over 24 hrs. You can tap into an A/C vent for the room? Not sure what latitude you live, but it can get 120+ in an attic. Trying to overcome those temps, your going to need a/c. during the hottest part of the day the room will be 85+ with a/c. The most important element in an attic build is ventilation.