So I was just having a discussion with Jesse Coombe regarding the Warhammer 40k mod we are planning and we got to talking about terrain, and how it should be handled. I thought it might be relevant to your discussion here.
the basic idea is this that stars equal "city" sites. these are the only terrain that you can build cities on. your cities then represent not actual cities but star systems controlled by your faction. There would be different types of "stars" to represent the various types out there, i.e. yellow, red, blue, white, giant, huge, large, small, dwarf, and to allow for various values, obviously large yellow stars would be the best place to build. The coast area would be rocky planets that surround your star and make up the interior of the star system. (some areas of coast should be made to look like space so that the star is not surrounded by a ring of planets) the sea would be gaseous planets and would make up the outer parts of the star systems (the same goes for sea, some areas of sea should be made to look like space so that the star is not surrounded by a ring of planets).
Resources in the coast and sea could be asteroid belts made of different minerals or space worms for food, or something like that.
This would work really well for user created maps, but less well for randomly generated maps. it would work best to use the small land mass option with a high water to land ratio.
As it stands now, though the space graphics are the best I have seen for any civ mod, the "planets" look a bit odd as continents.
There was a civ2 mod, based on MOO2 that had something along the lines of what I am talking about. I think you can find it on apolyton, not sure if they have it here as well.
If anybody has the Star Wars Rebellion game, that has a great map of the star wars galaxy. it also has some leaderhead images if I recall correctly.
by the way, the site looks great.