Basically to make the sequal story arc work it has to be a massive galaxy defining conflict that is dependant upon the force in some way, that most importantly has thematic links to concepts introduced in the original/prequels. However it cant simply be a "the mean ole empire is back with Palpatine 2: electric boogaloo!" since that would make the OT absolutely fucking pointless in the grand scheme of things (as the original EU kindly demonstrated like 10 fucking times in a row). Pretty much all ideas I have come up with/seen others come up with tend to be variations of the following four scenarios
- Jedi and the light side go bad: After decades of peace they wind up becoming corrupt/fanatical without the dark side to counterbalance it, causing them to overthrow the new republic and become full on quasi-religious dictators, leading to the sith being reformed as a resistance (an ACTUAL resistance, not the shit in the movies) against them. The thematic link would be the fact that Palpatine was (unknowingly) right all along in an irony to end all ironies
- Anti force conspiracy (ala KOTOR 2): the main villain, tired of how the sentient force dicks around with everyone and causes mass suffering for its unknowable goals (that inevitably get undone and restarts the cycle) decides to declare all out war against the force in order to break its hold over the galaxy and prevent more bad shit happening becuase of sith malevolence/jedi overzealousness. The thematic link is the fact that after the jedi help cause the empire, and the sith ruled the empire, surely some people in-universe must be questioning whether the whole force thing is a good idea
- Extra-galactic threat (like a non terrible vong): basically something invades the galaxy from outside that is utterly alien to the setting and the force as the characters know it, which causes absolute panic before the various factions unite against it. Also a chance to introduce other sci fi elements to the canon (i.e. lovecraft and shit). The thematic link would be the reminder of the fact that this is a sci-fi setting, and thus even those within it are unaware of the various mindbreaking and utterly alien shit that exists outside the borders of their galaxy
- Jedi/force/sith/whatever becoming obsolete: in the face of massively improved tech, force users are no longer special or important since any schmuck with power armour can take them down with ease, leading to jedi and sith order disbanding and scattering to die off quietly until the force itself begins to empower the survivors to even more ludicrous levels in order to combat some threat to all life which allows them to regain their place in the galaxy (think Jedi on the level of big hitter superheroes fighting legions of 40k level badass supersoldiers). I mentioned the thematic link before but basically what that bad hairdo guy on the first deathstar said about how the force was nothing compared to the might of their new technology, but actually correct this time.
Since the "dark side force is bad" arc has been taken in OT/Prequels, a "light side force is bad/anti force is bad/unconnected to force is bad/more powerful than force is bad" arc would actually take shit in a new direction.
