Energy Considerations: The real limitation might not be mass but the energy required to sustain the solidified light structure. A craft of monumental size would need an equally monumental power source, possibly drawing energy from quantum fluctuations, zero-point energy, or stellar radiation.
Adaptive Spaces: Within the craft, its light-based structure might adapt dynamically, creating spaces for living, agriculture, or recreation as needed—almost as if the vessel were alive and in constant dialogue with its inhabitants.
Habitat Stability: The structural composition could shield against cosmic radiation and micro-meteoroid impacts while also supporting atmospheric pressure to mimic Earth's conditions.
If we think even grander, these crafts might scale up to a size where they could encapsulate entire ecosystems—or even act as artificial biospheres drifting across the cosmos.
In terms of holding an atmosphere, advancements in photonic materials could produce a vessel strong enough to maintain the delicate balance required for breathable air and human life. The idea is audacious, but within the infinite realms of possibility, it just might be achievable.