Sounds interesting. The Matmos mod ands in the kind of ambient sounds you are talking about. I like the idea of solar and lunar eclipses and proper moon phases (Its sort of in the game but has no effect on light as far as I can tell) I'm not so sure about UFOs and comets and such. I think an enhancement mod to make things more realistic would be fantastic but adding things like UFOs I think may ruin it. Unless of course you made a proper UFO mod. For an enhancement mod I think it would be a bit too much. Or better still add options to turn off individual features from an in game menu.