While there will be tech that allows creation of Atlantis-sized mobile stations, wasn't there some technical restriction on dreadnought+ size ships entering atmospheres?
Those limitations basically come down to:
- Takeoff thrust
- Structural Integrity
- Ground pressure
The first is solved via sufficient Repulsors, the second is solved by PI's superior material sciences, and the third is solved by designing the ship such that it's ground pressure is minimized.