O'Neill had the right idea.
Imagine large rotating space colonies, each holding tens of thousands of citizens, in orbit around Saturn, Uranus, and Neptune. The magnetic fields of the planets would protect them from radiation, and the amount of organic compounds and volatiles in the various rings and moons would supply them with everything needed.
I imagine a future with multitudes of independent city states floating in the vastness of the solar system. Every conceivable cultural and political/economic setup could be tried.
