In 4.0 the devs break the established precedent of 2.0 and 3.0 by having the hub city only be fully accessible at the end of the story and instead putting the vendors temporarily in Rhalgr's Reach (even though no one would miss them let's be real. like let's be really real no one uses the vendors in major cities.). That city is, of course, Ala Mhigo proper. In fact, the whole expansion is solely Ala Mhigo focused. Instead of the 3 far east zones, we get an opportunity to throw in just a few more Eorzea zones, such as the home of the warriors in Abalathia's Spine, or maybe West Shroud or Coerthas Eastern. Exploring calamity-bombed zones would be a good way to add in some foundation to start talking about what the calamities actually are.
In 5.0, you guessed it, Doma's time to shine. Same case, city not accessible until the end. Kugane becomes the end hub. Yanxia gets 2 or 3 zones (Fanged Crescent, anyone?), with the opportunity to add in the Ryakgyr Peninsula, The Nhaama, and/or the Dalvalan Grath ("Why not Nagxia?" save that for a future expansion). The patch quests could actually continue quite similarly, with Tsukuyomi, The Burn, and Ghimlyt Dark. This time, though, instead of jebaiting us with the soulsnatching, Ghimlyt Dark functions as it SHOULD in that it acts as the gateway to the next expansion the way Baelsar's Wall did before Gyr Abania; the first zone of 6.0 is Ghimlyt.
In 6.0 we go to Garlemald and put an end to their reign of terror once and for all. Approach Ilsabard by traveling over land through Ghimlyt, but before we can make it through the Magna Glacies, we find that there's too much military presence between Ilsabard and Aldenard, so we then reroute and rendezvous at the hub city of the expansion; Radz-at-Han! We gain access to the two zones of Thavnair, north and south, and set up base in Radz as it's a neutral territory from which we head north to Garlemald through an airship disguised as a merchant ship. Before we get there we pass through Nhalmasque, a region long annexed by Garlemald that had been thoroughly ravaged. A great way to put the cruelty of the empire on full display. The end hub could then be dug out of part of the city proper, where we aid internal resistance. 6.0 ending at the very beginning of civil war after we kill Anima (and therefore Varis) would be pretty raw, I'll be honest, but that probably wouldn't be very realistic. I think a Garlemald expansion would be the perfect time to pull out the FF7 references, Midgar and Sephiroth's theme and all that fancy stuff.
This is a scorching hot nuclear take, but I think we should fight and "kill" Elidibus in the patch quests, specifically 6.3 to act as the "finale" of the Garlemald arc since the empire was created by the Ascians, "killing" the heart of their god, thus deactivating him and his protection, and restarting the doomsday clock without realizing it would be pretty raw. He'll be back though, I know better than to let such a major figure fade out so easily.
With Zodiark's aetherial barriers now fading, Exarch now finds it easier to start soulsnatching us; 7.0 is when we get Shadowbringers. This time, instead of rushing to save the first and return back to the source to resume holding off the empire just to find out they're conveniently destroying themselves so we don't have to, we have to race against the clock to start preventing the Final Days again. Otherwise, SHB can go on virtually the same as it did, only this time the lore it drops is a lot heavier because we had more time to build up previous knowledge. For example, we would probably already know that HydZod are primals. Going to Amaurot could trigger echo memories of the Final Days and give us a glimpse at the summoning of Zodiark and Venat formulating her plan. This also gives us the potential to have what the writers initially intended, which is Eden being the final boss. Sure, it might be Meteion-tier disappointment, but we could at least know Hades is yet to be defeated (and will be in 7.3). After the first is saved from light extinction, it's out of the frying pan and into the fire as we head back to the source and cracks are starting to form, blasphemies emerging. It's small at first, but worrying enough to know that we have to get a move on.
Welcome to 8.0, the first expansion in which the level cap is not boosted past 100 (or 99 if we want to go real JRPG) to represent that after all of our journeys we've maxed out our power. Now we're tasked to put it to the ultimate test as we fight against despair itself threatening to end all existence (though I would really prefer if it were localized to our galaxy, and we could take comfort in knowing that millions of lightyears out there are planets bursting with life, I just find that much better than something that insinuates an inane "humans r superior" message).
From then on it's all changes I've already talked about these past few months; Sharlayan guards knowledge about all of the past calamities and the sundering, which was given to them by Venat who guided Nyunkrepf as her prophet, we need this knowledge to fully know what we're up against. Elidibus takes a role in the story as a helper because PLOT TWIST we didn't actually kill him and we just deactivated Zodiark. He guides us to unsundered Etheirys where we get multiple zones, and carry out a storyline about helping them prevent the Final Days in their time thus creating an alternate timeline that we can then access through the engineered Crystal Tower's spacetime travel. The second mid-story trial can be Meteion, in which we defeat her before she escapes to become a galactical terrorist. Ultima Thule would be... cooler? Idk, the design of the zone just didn't do it for me. If it was placed in the center of the galaxy in front of a supermassive black hole I would absolutely lose my mind. Also, this is kinda minor but I would scrap Labyrinthos entirely and instead move outside Sharlayan to the Old World islands for the first zone of the expansion. Damn Daniel himself should be the first mid-story trial, as we try to stop him from hopping into Zodiark. After we return from saving the unsundered world, we have Elidibus hop back into Zodiark like a battery starting him up again. Zodiark finally speaks to us for the first time, and offers us his aid in the fight against the despair threatening our galaxy.
After the final dungeon, Hydaelyn and Zodiark join together and, with our aid in a scene that resembles the scene at the end of Praetorium when we "kill" Lahabrea, we unite for a single strike against the eldritch entity that finally ends it. Zodiark and Elidibus, having exhausted all of their aether, finally pass once and for all, and can die somewhat happily knowing that their world is saved in another timeline and they managed to finally put an end to the threat that started the destruction of their star in this timeline. Or perhaps Elidibus passes on after we challenge Hydaelyn and defeat her for the crimes of sundering the world and to free us all from her tempering, thus serving as the final trial of 8.0. Having lived to see her destruction, he decides retribution was somewhat properly enacted and he can finally rest. Now that the world is free of her thrall, free to determine their own future, things are Real Damn Good in the world, both here and in the alternate timeline. The end, but wait there's still more adventures to be had, blah blah blah, onto a bright future of gimmicky expansions we go!