I think KSP 2 will succeed or fail on fundamentals. Build a great core platform, and then release lots of DSLs that expand the game in ways that the player base might be interested.
Focus on quality and being bug-free. I know you want to add features, but the community can add features more easily than fix bugs.
Be excellent at physics; KSP has arguably the best physics engine of space games. It needs to stay that way. I don't just mean rocket mechanics -- everything. There's a definitely a threshold where realism intrudes on fun, stop before you hit that.
Be very extensible; Community mods are a major part of KSPs success. The more you can lower the bar (docs) for community development, and the more you can make mods stable across versions, the more the game will gain for free.
And that's it. Colonies in space, interstellar travel, resource management -- all those things sound like great DLC content I'd pay for. Why not get a rock solid base game out there now, and start collecting revenue off it?