Alright, here's what I mulled around last night while watching TLJ to prep for RoS: (this might get long, TL;DR at the bottom).
1. Snoke is Darth Plagueis, the Sith Lord that Palpatine talked about in RotS. However, he's not real, either: he's a Force Ghost that can interact with the corporeal world (similar to what Yoda does in TLJ). This makes him incredibly strong, as he can't be fought on the physical plane, but is essentially the most powerful Force user we've seen. Also, he isn't unceremoniously killed halfway through the movie.
2. Luke doesn't "run away and hide", he doesn't give up on the Force, and he doesn't pull a lightsaber on Ben. After Snoke turns Ben, Luke realizes that Snoke is more powerful than he is, and in order to defeat him (and turn Ben back to the light), he leaves the New Republic to search for the Ancient Jedi Texts. He doesn't take any way to track him, so Snoke can't find him; the map in TFA is to find Luke in case he's needed to return before he's ready.
3. Rey, Chewie and Artoo are sent to find Luke due to the events of TFA, but Luke can't find the answer to beating Snoke, and won't waste time training Rey. (You could also tie in Luke's insecurities about being a teacher here, as the last student he taught (his nephew) turned against him.) However, this is where Yoda pops in to give his old Padawan one more lesson: how become one with the Force, and battle Snoke Ghost to Ghost. He agrees to train Rey at this point, and while in a light saber duel, pulls an Obi Wan and has Rey strike him down, becoming more powerful than both of them could ever imagine.
4. Tie this into the Rey/Kylo Ren dynamic, which was the best part of the film. Have them keep trying to turn one another, with this being the pivot point on which the war moves.
Sideplots:
1. Ditch most of the slow chase that permeates the movie. Have the FO Flagship destroy the bridge of the Resistance's Flagship, but Leia uses the Force to hold the bridge together, allowing our principles (Poe, Finn, BB-8, Threepio) to escape. (This is where Leia dies, mostly due to the unfortunate passing of Carrie Fisher, but it's also a better example of how strong of a Force Adept she is). Holdo assumes command, and the Resistance escapes to Crait, with the FO on their trail.
2. Due to the New Republic getting blown up, the Resistance is running low on supplies and support. A new energy source is found outside the Outer Rim, and Poe, Finn and BB-8 volunteer to go get it; we get rid of the Casino storyline and the Holdo/Poe storyline, as well as keeping Holdo alive. This is where we tie Luke and Rey back in with everyone else, as you can end the movie somewhat the same, with the Resistance trapped on Crait, with Kylo Ren bearing down to end them. Ghost Luke shows up and holds off Ren while Rey helps everyone escape out the back door. Snoke, being able to sense Luke, ghosts to Crait, but finds out that Luke can now fight him, causing him and Kylo to regroup and retreat.
3. When Poe, Finn and BB-8 make it to the Outer Rim, they find multiple energy sources, but it's an armada of Star Destroyers being led by Force Ghost Palpatine.
This sets up Rise of Skywalker to be Resistance vs. First Order vs. the Empire, allowing for an epic battle between Snoke, Luke and Palpatine, while also keeping focus on the dynamic between Rey and Kylo.
TL;DR:
- Snoke is a Force Ghosted Darth Plagueis who can use the Force IRL, and doesn't get killed.
- Luke needs to become a Force Ghost to stop him IRL, but doesn't know this until Yoda shows up
- Luke trains Rey, but has her kill him to become a Force Ghost
- Poe and Finn go looking for supplies, but find the Emperor Force Ghosted on the Outer Rim
- Leia dies saving everyone
- Rise of Skywalker is a Triple Threat match.
Thoughts? We could turn this into it's own thread if necessary.