Powerplay is their introduction of Tier 1 NPCs. Tier 2 is probably coming soon. Tier 3 are already essentially in the game.
Although I think it's safe to say that tier 3 isn't totally finished, and I hope tier 1 makes some appearance outside of power play.
I don't think that PP is meaningless if we have major factions, I like the idea of sub-factions on a larger scale than minor factions, which are typically single system entities.
I do agree that having so much built around these "Tier 1 NPCs" while other, seemingly more fundamental entities like minor and major factions are so underdeveloped seems incongruous, but I think we can safely assume from Frontiers communication that there is more to come on those subjects in future updates.
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While I thought I understood 'major' and 'minor' factions, I have struggled with how 'powers' fit in. In my mind I have tried to draw parallels with real life - and still failed (maybe someone could explain).
From what I have read they can control up to hundreds of star systems and yet, isn't that what the major factions do..? Two different and yet simultaneous forms of government in the galaxy?
It's like, say, the CIA vs. the KGB - Major factions would be USA and USSR, minor factions are like, California or Cuba, and PPs represent the intelligence agencies: strong players in the scene, sometimes with their own agenda, but primarily beholden to a major power.
You can't really tell the story of the Cold War without talking about the CIA and the KGB - describing entities that got in between leads to a more interesting tale.