Remember that scale doesn't have to be exact in this game. We have to seek a balance between real scale and game scale. In which game scale is highly skewed and made for function more than accuracy.
We also could have randomized solar systems where we would not have to have the same planets we have for our solar system. This could also open up other types of planet terrains that are different than Martian or Lunar.
True. But shouldn't we have 'terrain map styles' for all our planets? I mean, eventually, we'd be able to explore and even colonize every planet in the solar system! Tech has few limits.
Mercury? Sure its hot but with effective shielding and temperature management we could put habitations there, but why would we? I suppose if we had a tech level that was converting plasma blasts from the sun directly into any material of our own design...
Venus? Yeah it'd be a hellish terrain but could certainly be useful for a lot of mineral resources, possibly exotic ones. After some terraforming to get rid of the overwhelming greenhouse effect there, its feasible it could become a very hot but otherwise not SO bad place, so long as you can dodge the constant lava flows or shield against them.
Gas Giants? Gas harvesting companies on levitating cloud cities? An 'air map' as it were? The natural gas sources here would offer tremendous energy for a wide variety of technological application.
Then we have some of their watery moons covered in ice that would make great fully underwater map environments (with all new alien animal life forms perhaps.)
Pluto? Great for mining - pretty much a full on map of lunar and barren and ice but a mappable location nevertheless. Good strategic spot for guarding the solar system.
I know we might want to keep our map count down - not sure what our limits will be there, but thats just throwing out some ideas anyhow.
lol 
