They could do what the SNAIL Racing League here on GTPlanet does for qualifying. Cars are on track for visual confirmation in case of lag, but in real life they'll just start from the pits. Each car goes out in 5 second intervals. This way no one is on top of the other, and you get them all out in a timely fashion. 20 cars, 5 seconds each, it will take 100 seconds to get all cars on track for Q3. It will be even less each time as drivers drop off.