We doing road maps to the end? Cool, I've got some ideas to lay out; some parts of the following will be obvious stuff, others will be wild conjecture.
Wano needs to conclude Luffy's battles with Big Mom and Kaido, leaving him 75% of the way to Raftel and 50% of the way to beating the Four Emperors. The breaks between acts show a number of things around the world, including Smoker's meeting with Vegapunk, but won't cut back to the Reverie until the very end. Jinbe is retrieved from Big Mom's prison either during or after the arc and joins the crew for real. Unfortunately, he's had years of his life taken, and is doomed to die within a year. Naturally, Luffy's victory over Kaido and Big Mom is global news and establishes him as one of the biggest names in piracy, not to be ignored. The Reverie ends with the Five Elders choosing to target one of the princesses they can reach in their holy land, either Vivi or Shirahoshi, which one is irrelevant, but both will be sucked into the conflict. The members of the Grand Fleet on location help protect the princess and ultimately send out a cry for help to the rest of the fleet, which converges and helps both princesses escape. Vivi cements her role as an honorary Strawhat by taking command of the Grand Fleet and coordinating it in a way Luffy never could. The Revolutionaries are rebuffed by a mix of the admirals, some new Vegapunk weapons and maybe some secret stuff from under Mariegoeis the Five Elders pulled out special for the purge.
The crew sets sail for Elbaf, led by Big Mom. Her time as an enemy is concluded in Wano, but she has too many plot ties to Elbaf not to make an appearance there. There are two possible reasons to travel to Wano. The first is that the crew learns the last Road Poneglyph is there, but the other is that Luffy, right when he should be in his prime, falls ill with the same disease Roger had. Chopper thinks he can cure it, but he needs an ingredient that can only be found there. The journey to Elbaf may be made up of several smaller arcs as Oda gets the last few ideas he can't wait on out of his system. Likely we'll see a huge number of places where Roger visited and people he met, resulting in a number of flashbacks. This is the last adventure before everything gets big and endgame-y.
At Elbaf proper, Luffy is incapacitated by his disease and the crew is given one last chance to show how far they've come, each operating independently of their captain. Likely, Usopp takes the helm. We learn Elbaf was once a gateway to the moon kingdoms, and the big obvious Yggdrasil tree we saw at the start of Big Mom's flashback was once a space elevator. Enel and his army are descending the elevator and act as the main antagonists for the arc. The crew ultimately chases off Enel and forges a peace between Elbaf and Big Mom. They do not travel to the moon but learn a lot of ancient history about the civilisation that was once there and the other, no longer there moons depicted on the Oharan globe. They learn how the World Government annihilated the moon kingdom and its allies on the other moons during the Void Century. The crew gains access to the last Road Poneglyph and learn that Raftel is under Mariegeois.
The B****attle of Raftel begins shortly after. The crew fights the Navy and its admirals at New Marineford over a number of days but are unable to punch through. Luffy finds Morgans has he tries to report on the battle and announces to the world where the One Piece is. This gets the attention of basically every old enemy and ally group ever featured in the manga. Pirates come from the corners of the world. Pirates come out of retirement. New pirates pop up. Vivi brings the Grand Fleet. National armies join the fight. Some of the accumulated forces work together, others fight each other. Every navyman ever featured is summoned to the last defence of the holy land. Blackbeard's crew arrive and cut swiftly through the battle, destroying everyone who isn't themselves. The battle ascends to the holy land properly and Pangea Castle is destroyed in the fighting. The Five Elders and Im pull a number of dirty tricks, including using Vegapunk's tech to make new cyborgs of the bodies of the moon kings, one of which was the original owner of the Straw Hat, but they are ultimately defeated before the final stage of the battle. Blackbeard takes advantage of the crew being distracted in their fights with the Celestial Dragons and their weapons and breaks through right to the heart of Mariegeois and takes hold of the One Piece first. Shanks is obviously going to have a part to play in this section, but we don't have enough information to say what at this time. Jinbe's clock will be nearly out by this point, and he will die, probably in a heroic sacrifice, at some point in this conflict. Maybe now, maybe in the next section.
In the Last Battle, Blackbeard activates the One Piece, expecting to be empowered by it. I subscribe to the theory that it will destroy the Redline and Fishman Island both to create All Blue. Maybe Blackbeard was mislead about this, and expected something else, but maybe he planned to use his black hole to draw in the power that was to be used for that destruction and become a human supernova. Either way, he doesn't get the instant win he hoped for, and his crew has to square off a final time with the Straw Hats among the ruins of the World Government to keep his prize. Luffy and Blackbeard are the last fighters still going, and the clock is winding down before the Ancient Weapon's explosion. Robin thinks she can disarm it, but Luffy decides the world needs the freedom that will come from the destruction of the World Government and the Redline. It will be a more interesting place that way, after all. But he needs to finish taking down Blackbeard to make sure he doesn't shut down the weapon or try to take its power again. The crew retreat and pass word along to the fleet outside to evacuate Fishman Island. Luffy beats Blackbeard but both vanish in the explosion of the Ancient Weapon.
The epilogue begins, showing how the world has changed and how the scattered crew has achieved their dreams. Luffy is remembered as the last King of the Pirates. We see basically everything and everyone one last time, but in some of these vignettes, a figure in the shadows in seen watching the old Straw Hat crew, getting closer each time he appears. When we get to the last crewmate, possibly Zoro, running a Wano school of swordsmanship, or Nami, putting the finishing touches on the first atlas of the changed world. there's a long build up to the figure's reveal. Of course it's Luffy, with an eyepatch, and the rest of the crew is with him already. He asks this last crewmate if they want to go on a new adventure.
Obviously, I'm not going to say this is all remotely accurate; predicting Oda is a fool's game. It's a mix of guesses based on the evidence and plot threads we have so far, subject to change as Oda offers new material to work with, and my own ideas and things I'd like to see. I look forward to people saying how glad they are I'm not writing the story