The only thing that 1.0 did well was the atmosphere as it was dying, and I'm not really sure how they would re-implement that for someone to experience. "The story" wasn't much to write home about. We hit most of the story beats ("investigate the Garleans" and "what's up with those Primals") in the 2.0 story, and "the content" was mostly just Garuda/Moogles/Nael and Aurum Vale/Dzemael Darkhold I guess, and we already have versions of those in the current game. At the end of the day, it was still like any other MMO where you had a multitude of mundane crap that you could do. I can only think of a few possible things that might interest people.
1) The only thing from 1.0 that I'd personally like to see re-created is the old Nael van Darnus fight. Its unique gimmick was its multi-floor fight arena (Nael on the bottom, DPS the falling meteors from the middle floor, DPS check on the top). I'm honestly surprised we haven't seen anything like that since then. Maybe there are technical reasons why that's no longer possible, idk. The only thing that feels similar about Turn 9 (since that's our current iteration of the Nael fight) is the donut AOE.
2) The last moments of the server. If you were in Mor Dhona for the last bit of the server being online, the place was just flooded with Garleans (and their mechs) to kill. I could see why people might be interested in experiencing this, but I don't see how they could do it justice. It wasn't content that was meant to be beaten, it was just a ton of mobs against a ton of players, and occasionally getting disconnected from the server due to the massive load, of course. If they tried to re-create it as a solo instance, it would really lose the impact, and it's also hard to re-create something that doesn't really have a "win" state.
3) The weird state of the world. Each patch bringing Dalamud, the glowing red moon, closer to the world. The eerie version of "Answers" that played on the overworld after the last 1.0 patch, instead of the normal BGM. Urianger (back before we ever knew anything about him) randomly spawning at Aetheryte camps to spout weird doomsday poetry in his archaic way of speaking. (I am still salty that ACN doesn't use that weird rocket-launcher-lookin' staff thing he had equipped back then, by the way) Similar to #2, I don't know how they would ever re-implement this in a satisfying manner. It's not really content to be consumed, it was just... how the world was at the time. It didn't affect your day-to-day playing in any functional way, it was just atmosphere.
Aside from that, I don't think the story had much to remember (I certainly don't remember it). I remember both Garuda and the Moogles playing a part, but those are already present in the current game. The rest of the stuff that I recall isn't worth re-treading (either because we already have something similar, or because it was garbage).
I remember standing around at Aetheryte camps at predictable times to see Atomos spawn and have a mass of people slaughter it. That's basically hunts now.
I remember hamlet defense being a thing, but I never participated in it.
I remember chocobo escort missions, but those were dull as hell.
I remember sometimes while mining, my sledgehammer would appear jutting out of my elbow for some weird reason.
I remember massive maps, where most of the areas were full of copy pasted scenery and nothing interesting.
I remember a terrible market system. Corridors full of lifeless retainers with bazaars, constantly shifting their weight so as to not appear completely still.
I remember a materia overmeld system that would cause you to lose your item and all of the materia on it if you messed up your overmeld.
I remember having additional underwear slots (body and legs), despite the fact that there were only two kinds of underwear (Hempen and Cotton).
I remember the crafting system being very cryptic/obtuse.
I remember a whole bunch of terribly-designed game mechanics (fatigue, magic/weapon skill ups, attribute allocation, etc.)