Sean Raymond, planet formation guru, blogged on an incredibly audacious physics based possibility – a maximally packed Solar System, with 416 Earth-mass planets in the Habitable Zone. Such a system requires 8 rings of planets, with 52 Earths in each ring, four rotating prograde around the Sun, and four rotating retrograde.
The number of planets packed in each ring depends on the mass of the planets. Smaller planets can be packed in greater numbers in each ring. With a mass of 0.01 Earths each, thousands of objects can be orbited stably around a Sun-like star. British philosopher, Olaf Stapledon, in his aeons long Galactic saga, “Star Maker”, imagined disks or clouds of artificial planets surrounding stars. Such systems later inspired Freeman Dyson to imagine how intelligent life would rearrange the available mass in its star system to maximise livable area. Or, better, volume.
Rather than planets, large habitable gas-filled volumes could be constructed. These would be tens thousands of kilometres in diameter yet mass only as much as the Moon. They would be too big to hold in the gas via structural strength, instead using the mass of their outer shells to provide counter-pressure by their own gravity. Also known as Gravitational Space Balloons.