However it might be implemented, the OP is absolutely correct...
The ability to "build" cannot be overstated as an attraction to any game. It is human nature to want to explore, but right after that comes settlement/building. Rust, even though it was a pre-alpha game, was an enormous hit simply because it allowed players to gather resources and build structures they could call their own, in a possibly dangerous and hostile environment.
I do think that the OP is making a bit too complicated with the idea of alliances, factions, etc. Player-built outposts could be basically neutral, offer safe harbour and supplies to any that visit, and a source of income for the "owner".
It would be incredible if a team of people could take a Type-9 and the requisite "build modules" and a number of other ships and build an outpost 10,000LY away from Sol. I would not expect players to build a full station with shipyards, etc, but with enough effort an outfitting ability would be very useful.
If this game is to have significant longevity and a stable/growing audience, this absolutely needs to happen. Sticking to past paradigms will doom the game to an early end.