To revise my earlier post slightly, I think that settling or establishing colonies on even the easiest Other Planets (moon, Mars, LaGrange sites, asteroids) should be Abstracted: perhaps as a massive Project that allows you to extract new resources from one such destination, but doesn't require you to actually 'play' on another surface/orbital platform, planet or moon. That keeps the game focused on Earth, which is complex enough for most of us, and can save the Interstellar Trip for an end game Victory Condition as the game franchise has done before.
And the Giant Death Robot is not a Futuristic as much as it is a Fantasy unit. All the trends in military technology of the last twenty years are leaning towards smaller, lighter, more mobile, stealthed applications. Making a Dreadnaught on land like the GDR will result in the same fate that befell the dreadnaughts of the Italian fleet in 1940, the US Pacific Fleet in 1941, and the HMS Prince of Wales and INS Yamato: sunk by enemy air power. The early lessons of the Ukraine 'special action' only reinforce this: there are just too many weapons that can take out anything they can find, so watch: for the next decade the major military advances will all be in the area of Not Being Found - stealth for drones, tanks, and infantry as well as ships and aircraft, and even more capabilities to take out enemy heavy weapons like artillery and tanks once identified. The reporters bark about Hypersonic Missiles, but the real Superweapon will be the stealthed Drone, that can search out enemy depots, HQs, tanks and artillery wile remaining immune to enemy weapons, and attack them without warning.