I would, eventually, love to see NPRs making sub-system claims on areas they have settled out to share, like a home system (or other system where both want colonies, if diplomatic relations are good enough).
Much like the exclusion zones you placed around the Solarian bodies: "Everything in this quadrant of the asteroid belt is mine, stay away. This planet and its moons are mine, stay away. Everything around this star in the binary is mine, stay away. But if you do that, I don't see any reason we can't live together peaceably."
Obviously that's post-release pie-in-the-sky stuff, and probably wouldn't come up very often in a player-facing fashion anyway except for multi-faction starts.