Brandon Rhea at Star Wars Fanpedia writes a little about Luke Skywalker and his freedom or captivity and how it relates to a super weapon:
It appears that this super weapon is a naturally-occurring, planet-based weapon, and Luke is being held nearby. He and his captors, whoever they are, know that if Luke uses his uber-Jedi abilities, the weapon will be triggered—potentially destroying an entire star system. And so Luke has remained there for all these years, not using his powers and cutting himself off from his friends and family.
If accurate, it certainly presents an interesting stalemate for Skywalker. That said, what is the viability in a weapon that destroys the system it is in and presumably itself? I know very little about the “super weapon” myself. The concepts I have seen that relate to the idea are outlier pieces and don’t really scream “super weapon” to me. One looked like a sink hole almost exactly identical to Utapau in Revenge of the Sith. Another looked like a factory on Mustafar, mostly unfinished but with giant flags hung outside it. Strangely, these two pieces were important enough to make their way to Pinewood where another source independently identified seeing them. Weird, right?
My personal impression is if there’s accuracy to the rumors, its more of a mutually assured destruction scenario. You cannot point the weapon at another system like the Death Star. But the weapon keeps Luke Skywalker from being active in the galaxy. Good cannot run rampant. So eventually, something “awakens” in for good and evil outside the past generation’s Détente. Its an interesting concept. It would make both rumors true that Luke is in self-imposed exile and a prisoner at the same time.
In that scenario, Luke would be trapped there until rescued by those powerful enough to rescue him, but weak enough to not activate the weapon. That said, it sounds really confusing. It seems like a difficult idea to relay on screen to an audience that just wants to see Millennium Falcon again and is still confused by Midi-Chlorians fifteen years after the concept was initiated on screen.
All I know with some certainty is that Luke Skywalker is unhinged and a bit off-kilter in this film. Can these rumors interface? Is Luke Skywalker’s sanity threatened by having intense power and not being able to use it? What Star Wars Fanpedia has presented is interesting to say the least. It doesn’t like up with what I have heard but I’m also really in the dark on this “super weapon” stuff so far.