First of all, what most people make is ruins. Ruins that are set in random deserts in the middle on fucking nowhere, and that doesn't make much sense either. if i were to make this some sort of ruin it would certainly not look as good, and i'd have to come up with way more background to the map to find a reason to block off access to broken walls and such. And i don't feel like designing a city, not with the current textures.
Second, who said the map is set in space, that's just the night sky. some thousand years ago you didn't have lamps to litter the sky and see only a couple of the brightest star's, there were more to see than the eye could count. In my opinion, the skybox matches these ancient years just perfectly

the flag bases are a bit unique, but the height is 2 cube levels. because the height of the second layer is really small, in addition to the cube size used, its impossible to select it unless you view it sideways. this happens in many cases, even if the geometry is on the air, you could select the empty space behind the actual cube >_>

as for the jumppads in the middle of the map, they were merely a small addition to the accessibility oh the higher walkway from the lower plateau, though their pushing should be removed since it tends to bump you on the wall if not carefully positioned.

as for the clipping i know of a way to smooth out the corners all the way to the top. water in the fire cauldrons will also be removed to improve performance, since looking the overview of the map from the bases' ledges drops the fps count considerably for this possible reason.