Personally I think the surface bases are likely to be thargoid ships, but from jameson's description, they are too small to be hive ships, you cannot really see interceptors docking there, there simply isnt room for them to land/dock/latch on. I also think these entities are getting repaired from mycoid damage, mycoid ofcourse being the secret biological weapon humans used in the first thargoid war to end it. A weapon of mass destructions we pulled the trigger on. Now if you look about these sites, you can see a beautiful iridescent scalar structure to their "skin", where the scavengers (thargoid skimmers present at these sites) are "working" they are focussed on abrading yellowy -like looking sections of the structures. These yellowy bits look a lot like an infected wound, infected by mycoid maybe?
Tinfoiling asides, the constant thursday/thargsday action during server tick is a pain, it would be much more engaging if players could attempt to repel the thargoid interceptors attacking the stations. It would be much more engaging if we got to see things happen rather than just the aftermath there of. It'd be much more immersive if we (eventually) got to see these downed for repair from mycoid damage, or slowly being grown on the planets surface, hive ships rising.