I’ve traditionally run Orphan Vessels as NPCs, because I like to highlight their sentience and non-pliability in the story.
However, you’ve hit on two of the optional rules outlined in the back of the full book: Macromoons are larger regions of space the multiple moons exist inside of, and which layer on top of the interior moons. Micromoons are smaller (but important) areas that are are distinct enough to have their own sentences.