I agree with everything there entirely (except the 3-6 planets) but yeah only thing I can imagine that would make sins more enjoyable is a more realistic looking space. 

The biggest thing I want with regards to Galaxy Forge is not in Galaxy Forge itself but rather the game itself.  This game desperately needs an auto-download function for custom maps, otherwise they never get played unless the map's author or a big fan persistently advertises the maps and helps the other players figure out how to install the maps.  Heck, perhaps some sort of a built-in custom map download and installation interface that players (in single or multiplayer) could use to browse and download approved custom maps held at some server would be a good idea.  (For an example of something like this, Ironclad, see the freeware game "TripleA", where the game will let you browse through custom maps stored at various URLs and then auto-download and install them.)

Dead, and gone, then dead again, then ... wait.