It looks a crap ton better than ANY other racing game/sim has had night lighting I've seen. It's a great start, and If we had a release date I'd already be planning on bringing up a 12 or 24 hour endurance race event or series with 6, 12, 24 hour races.
Of course, testing is needed to make sure there's no issues; but having the sky not change isn't an issue to me...if the light from the sun goes below the horizon like it really does, and perhaps even program in moon phase, that will bring the immersion. Westhill, Kyoto, Fern Bay would be largely pitch black with no nearby major town causing lighting pollution in the night sky to reflect back down, only lights installed at or near the track would give vision points. The lights already on the start tree is a good start for the flag lights...projecting the light output is a big issue I'm sure.
Great work so far, can't wait to see if this becomes a reality to us end users!