Generally, the various guidelines about big stations > little stations > surface bases > surface settlements work pretty well, because if the system was entirely procedurally generated that's the order things would have been added in.
If there's a reference in the timeline to a CG adding the Orbis after the 2.0 release, then this would definitely be one of the exceptions.
From what I'm told the Pleiades was largely custom made.
Seems in this system (from what I can piece together) it was:
1. Large Orbital (sometime before Jan 3303, not sure of exact time)
2. Both Surface Settlements (April 3303)
3. Smaller Planetary Base (April 3303)
4. "Two new outposts", but there is only the Larger Planetary Base unaccounted for (August 3303)
References:
https://canonn.science/lore/
https://elite-dangerous.fandom.com/wiki/Elite_Dangerous_Timeline
The war that kicked off right after 3.3 patch landed (pending that first day) had us defending the larger of the two planetary bases against the controlling faction would put up the smaller of the two planetary bases. As far as I can tell there was 3 already stations created in the system before the smaller planetary base was created and the controlling faction own one of those(the Large Orbital). Which suggests that "oldest asset" isn't the approach. In this situation but "Lowest Value" asset does work as the two Settlements were owned by other factions making the small planetary base the lowest value vs the Large Orbital.
Maybe the assets were created behind the screens, and the story feed them out in a different order than they were actually created and dated behind the scenes....but if that is part of the mechanic how would anyone work that out......is there any reliably incrementing ID number we can reference?