I’m remaining skeptical of a ‘tech-only’ explanation for Orison, else in my mind you would just have that tech float your shipyards somewhere more convenient. Why develop the tech to float in the fortuitously breathable atmosphere of a gas giant when you could find a nice flat plain on a similarly habitable planet and then keep your worker accommodation, storage yards and other factories cheap on the ground and just float the drydocks above? Why convince people to move to a platform over a bottomless pit when you could set up your factory in/near Tram and pay the locals next to nothing?
My current headcanon is a particular atmospheric composition granting a high level of buoyancy forces, e.g. replacing Krypton rather than Nitrogen in the air, which would still be safely breathable but provide about 2.5x the buoyancy for floatation tanks built into the platforms. Even more, if it’s a higher pressure environment (with lower % of oxygen and carbon dioxide to keep the humans and plants happy). That could make the anti-grav tech economical to use safely and extensively in a way that other locations cannot support, consistent with the relative uniqueness of Orison…unless there are other places like it that we haven’t been told about yet. It also helps explain how the whales keep aloft.
It’s not that important really. It’s a floaty city that looks good floating – what more would we want? I only really have thought about it because I’m considering making a machinima-style video about it in the style of a 1980’s corporate orientation film, where an upbeat PR officer explains why the city is safe to visit.
I can’t answer the tech questions though I love your speculation. Crusader as a company builds their ships below the platforms, obscured from corporate espionage agents by the gas giant’s clouds.