Originally a basilica was a Roman building with purely secular functions. A basilica typically had a rectangular floor plan, and contained a large hall. It principally served as a public meeting place for conducting business and legal affairs. The basilica of Trier gives a good illustration how a classical basilica looked liked.
Each Roman city had its own basilica, and without one, a settlement would not count as a city. Because capacity of a basilica to contain a large number people, it served as the center of civil society. Space settlers should consider to build new basilicas in their cities. And not in the last place because a basilica is an architectural enrichment of a city.
What functions should such basilica have? First, weekly services can be held there, probably each Wednesday. Such services could contain the following elements: a lecture on a philosophical, scientific or cultural subject by a qualified speaker, some music, and a drink at the end. Secondly, the basilica can be used as a room for temporary and permanent expositions of works of art.
Thirdly, people should be able to rent a basilica for their weddings, celebrations, memorial services, meetings and conventions. This would raise the revenue needed to maintain the basilica. The management of the basilica will have to make proper arrangements for renting the building.
As a special service, below an image of how the interior of an O’Neill cylinder might look like.