What we're seeing is the process by which Thargoids grow their ships - in the case of these larges "bases" we are seeing the creation of capital ships.
The centre of the base is the "seed", populated with eggs which will hatch once the ships has grown to a certain size to provide the crew.
We know that the Thargoids are able to leech metals and minerals out of the soil with barnacles, so it isn't that much of a leap to say we are seeing the same process on a larger scale create ships.
I agree.
With recent events we have discovered that the Thargoid ships are, in fact, living beings; they posses four hearts & to destroy the ship, you must destroy the hearts.
All living things, alien or otherwise, are born or birthed somewhere - I believe that the barnacle sites are 'birthing sites' for both the Thargoid ships and the required crew to 'operate' them; the internal vents providing a terraformed ammonia rich atmosphere that the Thargoids need to survive, once the ship has 'grown' or matured enough to allow the eggs to hatch.
The interaction between the Thargoid ships and the planetary barnacle sites themselves, I think is either a case of 'activating' or 'awakening' the ships growth or perhaps more likely, feeding them - they are after all alive and all living beings require some form of sustenance to survive. A kind of 'mothers milk' if you will.
It is perhaps not too far a stretch then to theorise that, just maybe, the areas of space where all these Thargoid related discoveries have taken place are actually one giant nursery & possibly even 'sacred' to the Thargoid race. If this is the case then maybe, we the Human race are now seen as a threat and the Thargoids are trying to protect their nurseries as any creature would if they felt that their young were at risk.
What also, of the Thargoid races lifespan; did they perhaps 'seed' their nurseries millions if not, billions of years ago, before mankind had stretched themselves to the stars. Are we in fact, in essence a younger race 'invading' their territories and threatening their young maybe even their entire existence?
I also think that something worth studying is this; Thargoids seem to be an eusocial 'insectiod' race, if we look at our own eusocial insects on Earth we see an alien world with an incredibly complex social structure with a distinct 'caste' system - each has a specific role to play and so I think there are probably many different variations to the Thargoid race that we have not seen yet.
It is possible that humans are alone in this concept but, maybe there is a division between warlike and peaceful castes, possibly even a spiritual division but, that's looking at things from a very human perspective!