I love this game, but as a new thought that could enhance the overall feel of a Sci-fi setting, add more Planet skins so that only a "few" planets look alike instead of "a dozen".
An added idea, the planets skins could reflect the Class Levels.
Maybe crap level planets look like Rockballs with some water.
While high level planets have articulate landmasses with details, full of islands and nice details, to make them seem like they could be their "own" homeworlds.
When I encounter a level 16 planet, it should like it's own Homeworld.
This will add an element of, "Hey, I remember this planet" and this will make the Planets seem more "Alive".
I don't think it's out of reach personally for the next installment, but what would I know, I'm not Stardock.
Regards,