Every faction, PMF or otherwise, has a home system which it can't be retreated from, and which it will ordinarily be present in (though Frontier can hand edit faction placement how they like and the consequences of a faction not being present in its "home" system are very subtle)Do PMF's have a home system from which they cannot be removed from?
(I assume you mean Live rather than Odyssey here, since the Thargoid War is also there in Live Horizons)I have seen various arrangements between various PMF's over the years to not challenge ownership of an owned system.
As part of the 'new' Thargoid Odyssey system it is possible to remove a faction, including I assume PMF's which you have stated return once the Thargoids have been removed.
This double instancing indicates the Odyssey 'overlay' DLC is divorced from the underlying BGS and the original states still exist.
In a very old (pre-Odyssey!) livestream, Frontier staff made reference to there being four BGSes: Political (the one players think is the BGS), Economic, Outfitting and Thargoid. They've always interacted with each other to some extent - e.g. a Boom state in Political improves the modules available in Outfitting and changes prices and quantities in Economic. Update 14 obviously extended the Thargoid Simulation substantially.
Any Thargoid state applied to a system suspends all Political state and influence movement in that system (this isn't the only way this can be done; Frontier have various forms of "lock" that they can also apply by hand to prevent some or all normal Political activity, and all other known forms predate Odyssey). Under Thargoid Control state the factions themselves apparently disappear, though return with their previous state and influence if the system is recaptured.
Frontier could do that, certainly - but whether any particular post-Odyssey change is required is probably something we'll never find out: the BGS rewrite in 3.3 was extremely substantial, even if it didn't directly change any factions.Does this mean that at one level the BGS can be overwritten completely resetting the state of the Bubble? If so, then my conjecture is valid that a new BGS using the Odyssey system can be used to reset in line with 'emergent gameplay' PMF's.
Not quite a BGS failure - it was an entirely normal outcome under the very early versions of the BGS, where a faction expanding out of a system would displace a faction from that system into its original system. It's not clear why it worked like that but it meant that when the Pilots Federation expanded out of SD a few times, they brought other factions in.The thought experiment would be the removal of the 'Goats' in Shinrarta Dezra who once were I believe were a PMF which due to a BGS failure got access to SD and therefore impossible to remove.
Since then, the Pilots Federation have been converted to a non-influence faction (which hides them on the system-level displays but allows them to retain station and system ownership) and the rules have changed so that expansions aren't swaps, so you couldn't do the same thing nowadays (the other two NPC factions which aren't the Dark Wheel got into Shinrarta in the same way)
The PMF in Shinrarta isn't technically impossible to remove, either - there are four factions in the system, so the Retreat state could be started if it got below 2.5% influence. It's just that passing player traffic through the system is huge, so doing that is extremely impractical even should someone want to.