[@Arawak]
With the new world details, it would seem that Ezra is indeed the most appropriate location for what I have in mind. Would it be reasonable for a custodian base on it to contain a small subterranean artificial ecosystem (a primordial, extremely rudimentary one - say mid-Cambrian or thereabouts in terms of Earth equivalents)?

On a related note, should custodian drones have a definable purpose, or can their intent be something completely esoteric, known only to their vanished creators?