Here's a parallel question about player minor factions.
If a pmf is exclusively xbox, does a parallel faction in the pc universe get created ...
Yes. The BGS is shared across platforms
even though no pc players "own it".
No players ever "own" a faction, other than the right to name it.
If a pmf is dead (no players are actively supporting it), and no squad exists for it, can you pirate the faction - create a squad with the name of the faction and essentially operate the pmf without official handover?
You can do that with any faction, PMF or NPC, supported or not, at any time. A squadron can only align with one faction, but multiple squadrons can choose the same faction.