I'm not sure how GG handles skyboxes as I've never messed with them, I've just been waiting for those features to evolve, but isn't a skybox or sphere simply an entity? Could it not be spawned and or destroyed/hidden via script (of course, resources would be sucked doing that)? Forgive my naivete if my suggestion is way off base!
Desktop: i7 4770@3.4Ghz, 12GB RAM, Win 10/64, GeForce GTX 1080, 1TB SSD, 1TB HDD; Laptop: i7 4800MQ@2.7Ghz, 16GB RAM, Win 10/64, GeForce GTX870M , 1TB SSD.