Here’s what the last Jedi should’ve/could’ve been:
The movie opens with star destroyers… then Snoke’s gigantic ship appears and overshadows them… masked Kylo enters Snoke’s throne room where he is reprimanded for being bested by Rey. He belittles Kylo, which angers him and makes him more powerful. Kylo tells Snoke the Resistance now has the map to Skywalker. Snoke tells Kylo that Luke must die and to bring Rey to him. No exceptions, no excuses.
Luke’s Island. Luke meets Rey, who tells him about Kylo… Luke realizes Kylo is his doing and senses Rey’s potential with the Force. Feels compelled to train her to confront Kylo.
Luke trains Rey alla Yoda in ESB. Yoda and Obi wan appear to Luke and Rey to tell them the dangers of confronting Kylo and the seduction of the dark side. He explains to her the depth of the power of the Force. During training, we find Luke is having nightmares at night… tempted by the darkside, which is why he went into hiding… to stay away from people he cares about, in order to prevent them from being hurt by him. Luke, by the way, has mastered the force, which makes him very dangerous and scared to death of what could happen if he turned.
The Resistance have escaped the base from TFA and are now traveling to an abandoned rebel outpost on the Salt Planet. En route, the first order finds them and attacks them. Space battle ensues. Resistance bomb run on the Destroyers and the Dreadnought. The Resistance succeeds in blowing up the Dreadnought, but most of the bombers get destroyed. Amidst the First Order fighters in one particularly daring and skilled fighter - MASKED Kylo Ren, who destroys multiple Resistance ships, most importantly… Leia’s ship… killing her. When it happens, Luke feels it (while training Rey on his island) and falls to the ground.
Luke is sent in a comatose state. Rey doesn’t understand what’s happening but feels compelled to care for him and stay by his side. While caring for unconscious Luke, Anakin’s ghost appears to Rey and gives her the history of the Chosen One and Luke and Leia.
Rey has a vision of her friends in trouble and feels compelled to leave Luke with Chewie and R2, in order to confront Kylo and Snoke. Anakin’s ghost warns her not to go, but she leaves anyway.
Rey flies the falcon to snokes ship and allows herself and the ship to be taken aboard Snoke’s ship. Kylo meets her and takes her to Snoke. Snoke tries to seduce Rey. He tells her the history of Palpatine and Vader, thus revealing he is Darth Plageus and has orchestrated all events leading to this moment. Kylo senses Snoke has used him to get to Rey. His anger takes over as he attacks Snoke suddenly. Rey takes advantage of the moment and joins Kylo against Snoke. They fight Snoke’s guards first. Once the guards are all killed, they face Snoke, who uses force lightning as well as a kyber crystal ring that creates a saber made of lightning. They have an epic duel against Snoke but struggle to get the best of him. Snoke almost kills Kylo, but Rey saves him by cutting off Snoke’s ring hand and then beheading him. They both narrowly escape. Rey and Kylo share a moment where Rey tells Kylo to join the light side, there is good in him. He responds by telling her to rule the galaxy with him – side by side. Rey declines and escapes. Rey must now escape the ship. She fights a number of stormtroopers in the process, and then fights Phasma. Poe and Finn show up with a group of fighters to attack the ship and rescue Rey. They succeed. Phasma lives.
They bring Rey to the Resistance base, now on the Salt Planet.
Hux confronts Kylo, who tells him he is now the Supreme Leader – Hux challenges him. Hux is then force choked to death. Kylo is the new leader of the first order. Kylo gives speech to first order telling them the Supreme Leader has been assassinated by the Resistance and he will lead them in revenge.
Kylo tracks Poe, Finn and Rey and shows up to confront them on the Salt planet with walkers, star destroyers in the low atmosphere and the whole first order infantry in an epic ground battle.
The Resistance gets shredded. Finn dies flying into the battering ram, keeping the First Order from infiltrating the base. Most of the Resistance fighters on the battlefield are decimated. Rey is the unofficial leader of the the Resistance as she puts up the best fight on the battlefield, slashing up troopers left and right, deflecting blaster fire to allow her surviving friends to retreat back to the base. Just as it seems she is overwhelmed, Kylo orders everyone to stop firing on her and demands he be brought down to her. They face off… he tells Rey what could’ve been if she had joined him and how foolish she is. He tells her if she won’t join him, she must be destroyed. They have a showdown. Kylo gets the best of Rey and cuts her hand off… while she’s on the ground, he lifts his saber to finish her off – “you’ve left me no choice. this is the end… cousin…”
…then all of a sudden Kylo is lifted off the ground by a Force choke. Pan over to Luke. Now in his all black garb, he’s back and using Vader’s force choke. He tells Kylo it didn’t have to be like this. He let’s Kylo down and tries to reason with him. They have a heated exchange about the past, about Leia and Han… about the Dark side… Kylo tells Luke it’s time for the Jedi to end. They have an EPIC lightsaber duel where Luke DESTROYS Kylo and eventually cuts all his limbs off. In a rage from the fight, Luke lifts the walkers into the sky and slams them onto the ground crushing them, then pulls the star destroyers out of the sky, as he has flashbacks of Leia and Han, as well as Rey training. There are explosions all around. He is overcome by anger, destroying everything. Throwing troopers around like ragdolls. Through the smoke, Rey is yelling to Luke to stop and come back to the light. Luke collapses on the smokey battlefield. Rey holds Luke’s body on the ground, as the Resistance scramble over to them…. Next scene, they are in the Rebel base recovering…. Rey gets a new hand. Luke isn’t shown (but he lives on for episode 9) - Cut to Kylo in a bacta tank with guards. Movie ends.