Make Rey and Kylo siblings. Not mystery surprise siblings like Luke and Leia: establish in the opening crawl that Han and Leia had two kids, one of them turned to the Dark Side, and Luke abandoned his role as leader of the new Jedi Order out of guilt for what happened with Kylo. At the start of the first movie, Rey is a newly graduated from the Jedi Academy on Coruscant. She’s pissed at her mom, blaming her for Kylo turning to the Dark Side, and for her marriage to Han breaking up. She also thinks she’s dragging her feet on doing something about the Imperial Remnant, which still holds a good chunk of the galaxy, and has been in a semi-cold/semi-hot war with the new Republic since the end of RotJ.
Rey runs off to join the Resistance, which is a group of freedom fighters from worlds still under the Empire’s thumb. She wants to find her dad, who quit his job as a Republic General to help run the Resistance. (Rey isn’t aware of this, but most of the aid to the Resistance is being funneled there by her mom, who due to political concerns, can’t openly support the Resistance.) She meets up with Poe (still a hot-shot resistance pilot) and Finn, who is a loyal Stormtrooper when they meet, but is forced due to circumstances to work with Rey and Poe, which gets him incorrectly branded as a traitor, and sets up an arc for him to eventually come around to embracing the ideals of the Resistance.
Kylo is working with the Imperial Remnant, but isn’t officially part of their organization, which at this point is purely military - there’s no Snoke, just some former Moff who’s decided he’s in charge now. Kylo is representing his unnamed master, but isn’t entirely trusted by the Imps. Using resources and intel provided by Kylo, they set up a big ambush designed to cripple the New Republic fleet and decapitate its leadership, but Rey, Poe, and a reluctant Finn rally the Resistance and prevent the plan from working. The Imperials take a beating, Kylo still kills Han, but the Republic is victorious.
At some point in the third act, Rey finds out that Kylo’s master is, somehow, Palpatine.
There is no Starkiller Base.
Second movie, the bloodied Imperials are absolutely stomping the Resistance, which exposed itself by helping Leia and the Republic in the last film. Despite their losses in the last film, they’re stronger than ever, thanks to Kylo showing up with a fleet of Star Destroyers of a new and unfamiliar design, all fully staffed. Play up tension between the Imperial Remnant and these new “allies,” who are very condescending and high-handed. Rey, knowing that Palpatine is back and is behind Kylo’s turn to evil, goes to find Luke and bring him back.
The movie still follows three narratives, slightly changed up: Rey is training with Luke, and having weird psychic Zoom meetings with Kylo. Poe is on a Resistance battleship, being chased by an Imperial ship that can mysteriously track them through hyperspace, but won’t close to combat range and finish them - Poe and his squadron are, instead, flying constant combat patrols to keep the Imperial fighter-bombers off their back. Finn is basically doing the Canto Bight sequence, but its set on Coruscant, and is more about the political apathy and self-interest shown by the Republic senators who refuse to help. Finn and Leia find out that some of the Senators are being bought off by Imperials to sandbag any military efforts against the Imperials. Included in this discovery are the details of the hyperspace tracking device the Imperials are using. Finn escapes with this information. Leia is killed helping him get it out, and in the process reveals the depth of corruption in the senate, but the entire Republic is thrown into political chaos over the revelations and the death of one of its more visible and beloved members. The information about the tracking device reveals that it only works if the tracking ship’s shields are down. Admiral Holdo, learning this, devises the hyperspace ram maneuver, a trick which would never work against a ship with functional shields (hence nobody ever trying it before now). The movie ends with the Republic in disarray, the Resistance reduced to a handful of survivors, and the Imperials poised to invade Republic space.
Third movie: the Imperial invasion of Republic space is well under way. It’s revealed (maybe in the climax of the last movie) that the new Star Destroyer design includes a miniaturized Death Star laser. Exegol and the secret SD fleet is still in - Palpatine, now a Dark Side Force ghost - set the planet up with a secret military research facility and the last extant Kaminoan cloning facility, and has spent the last thirty years making an unstoppable army of fanatically loyal clones all dedicated to the ultimate apotheosis of the Dark Side’s philosophy of destruction and entropy: he plans to use the Star Destroyers to cleanse all life from the galaxy by systematically destroying every planet capable of sustaining life.
Kylo and Rey have a final showdown, which leaves Kylo beaten and emotionally devastated as he realizes the extent to which he’s fucked up basically everything. Rey races off to try to gather enough of the surviving Resistance and Republic ships to invade Exegol and destroy the fleet stationed there before it can be fully deployed. Kylo, after a heart-to-heart with a hallucination (OR IS IT!?) of his dead dad, flies to the Imperial Remnant fleet and reveals Palpatine’s true plan to them.
On Exegol, everything’s going to shit. Rey’s getting her ass kicked by Palpatine, and is on the verge of succumbing to the Dark Side. The Republic/Resistance fleet is outmatched by the new Star Destroyers. Things go from bad to worse when they detect multiple hyperspace signatures, and a whole second fleet of old-school Star Destroyers start jumping in - only to open fire on the new Star Destoyers! Kylo has successfully convinced them that “killing all life in the universe” is not in their best interests, and they turn the battle against the Emperor’s forces. Kylo jets down to the planet surface to help his sister against Palpatine’s army of force-sensitive, lightsaber wielding clones. (Maybe the true origin of the Knights of Ren? If they’re in this one, they need to be a major thing in the first two movies, as well.) While he gives Rey cover, she has her showdown with the Emperor, who proves to be too powerful as a ghost for her to defeat, until suddenly she’s joined by Luke’s Force ghost… and then Yoda’s… and Obi-Wan, and Mace Windu, and Kanan Jarrus, and every other Jedi who’s ever had any face time in any Star Wars property, all on screen at the same time, and they collectively extinguish the Emperor once and for all.