I wrote something up awhile back and making this change across the films. Obviously a benefit would be that it might make the trilogy feel less like a retread of the OT. The downside would be the stakes might not be as high if the capital isn’t destroyed and the Republic isn’t in tatters and eventually conquered.
After Luke’s disappearance in TFA, you could establish that the New Republic and the First Order (a reunified Imperial remnant) have a truce, or peace treaty, to prevent another full-scale war. The First Order has no plans to conquer the Republic in this film. Their only goal is to find and destroy Luke Skywalker and the Jedi.
While Snoke isn’t a Sith, he could be referred to as a Sith cultist, an acolyte of the Emperor, a former Inquisitor, whatever. The Sith are gone, but Snoke wants to restore them.
Leia clearly objects to their goals, but the New Republic has a treaty to uphold and won’t interfere. So, Leia forms a Resistance cell within First Order space to sabotage the First Order and keep them from finding Luke first. The First Order does not destroy Hosnian Prime in this film. Instead, the third act is about Han and Finn acquiring the second half of the map from Starkiller Base (and rescuing Rey).
Even though the dynamics of the Resistance and First Order are similar to the Rebels and the Empire, this feud only exists in one half of the galaxy, and the New Republic still exists off-screen in the other half. While this might seem like a pointless change since they remain off-screen, removing the Starkiller super weapon, and the Republic’s destruction, allows the story to focus on this quest to find Luke and bring back the Jedi, differentiating it from A New Hope.
The Last Jedi would have the least amount of changes, structurally. But any reference to the Republic being destroyed, or the First Order taking over the galaxy within weeks, is removed. A reason for why the Resistance fleet doesn’t just escape to Republic space may need to be created. Perhaps the Supremacy is generating a gravity well, or we could add an interdictor to the fleet. Perhaps this could be a place for more radical ideas for the B-plot. When Leia refers to her “allies”, maybe she could be more explicitly referring to the Republic. Maybe they get a transmission from the Republic on Crait specifically saying they cannot intervene.
After Kylo Ren becomes Supreme Leader in TROS, this is when he finally enacts their plan to try and take over the galaxy. He is the main antagonist of this film, because Palpatine has not returned.
Perhaps finding Exegol was always Snoke’s goal after destroying Luke, and Kylo just followed through with it. Exegol could be established as where the secrets of the Sith lay hidden, and where Sidious left a lost fleet for his potential successor.
Once the Resistance gets this information, they share it with the Republic in hopes they’ll help them out. And sure enough, it is the entire New Republic armada that shows up at the end of the film to the end the war before it begins.
During the battle, Kylo Ren and Rey have their duel on the ruins of the Death Star. After their fight, Kylo Ren turns, and he orders the rest of the First Order to surrender, ending the war once and for all.