Alright, so:
Hi guys! New here.
That said, after a week of admittedly overblown apoplectic fury about what looked to be a time travel plot, in part due to how incredibly hard to parse the ending sequence actually is on top of Sephiroth's usual cryptic nonsense, I've come to the conclusion that very little has actually changed, plot setup wise, beyond two characters: Aerith and Sephiroth.
So, first off: Zack's not alive. He's dead. If he doesn't die, the entire plot, broad strokes and all, falls apart around him based solely on the fact that he knows Cloud's memory is incorrect and can explain the truth. "But Magos," you might ask, "what if he's just off screen doing a side adventure until Meteor gets summoned and he's not longer a danger to the plot?" Possible. However, the only real thematic or narrative contribution I can see that making to the characters or the plot would occur is Aerith escapes the Plot Reaper as well. Which is not happening. We can imagine ourselves in circles about infinite possibilities and unknowns but it comes down to one fact about this story we all love:
Final Fantasy VII is a story about experiencing, processing, and moving past grief. And Aerith's death is the moment of grief the game thematically hinges around. It is too important to remove.
In addition to that, FFVII is a deeply, deeply character driven piece. There isn't a single action taken by the party or the villain that isn't consistent with their internal motivations, and apart from Aerith and Sephiroth, there is no change to the people that each of them are following this ending, and there's very little actually changed about Aerith and Sephiroth as characters, only the information they have available to them.
So, first off: Sephiroth. Do I think him having the old script in hand and now free of the shackles of fate means he's gonna take this plot off the rails in some twelve-dimensional chess scheme? Absolutely not, because it doesn't really change anything in the macro sense. Even in the OG, Sephiroth was the only character with complete information about what was going on, and relied on that and his ability to manipulate Cloud via Jenova Cells to deliver the black materia to him and instigate his plan to escape his lot in life. The other thing to note about him is that he's both incredibly proud and a complete douchebag, certain in his position as the sole conductor of the events on his way to summoning Meteor. To be honest, I only see him getting more up his own ass now that he has the script. Not only are the broad strokes gonna play out in much the same manner as the OG, with concessions to adapting it to its current form, our boy in black is gonna spend his time rubbing the party's face in it, because the North Crater is already total, uncontested victory for him in the OG. He doesn't NEED to do anything.
Which brings us to our only real wildcard, Aerith Gainsborough, who at the end of Remake is now in the same position, roughly, that she was at the end of the Temple of the Ancients in the OG, her character development accelerated by visions provided by the planet via TIME GHOSTS and, importantly, her vision of the last stand of Zack Fair. Though expanded on in the Compilation, its clear even in the OG that Aerith is not as over her teenage love-interest as she'd like to be, and makes a point of that to Cloud in their date at the Gold Saucer, which is as much an excuse to talk to him alone as it is anything else, talking about her attraction in terms of how much Cloud reminds her of Zack, acknowledging his delicate mental state, and effectively asking to start over, as treating him as a replacement goldfish for Zack isn't fair (you may laugh) to either of them. Its a big moment for her as a character. Despite being, as the rest of the cast, a good person, she's also headstrong and inconsiderate of other people's feelings, exemplified best by her treatment of Barret's grief at the Gold Saucer and the fact that she aggressively flirts with Cloud even when Tifa, who she's shown to get on with like a tire fire, is in the room despite the fact that it makes her super uncomfortable and does not give a single shit in the process.
So, the considerate, patient, thoughtful Aerith Cloud speaks with on the gondola and in a vision after the Temple of the Ancients, who she developed into after learning more knowledge of the Cetra and what it means to be one at Cosmo Canyon and the Temple, and moving on from the 'normal' girl she wanted to be by making peace with her lingering grief over Zack by realizing Cloud's persona as fake and realizing she's been chasing a ghost, is the character that steps to the fore as the only obstacle to Sephiroth's goal of summoning Meteor. Armed with the White materia, and now the self-knowledge and wisdom needed to commune with the planet to use it, kind, headstrong, independent Aerith leaves the party and Cloud to finish the job to spare them from the danger to come.
And it's that headstrong, independent, caring nature that gets her killed.
At the end of the day, Aerith is still five-foot-nothing and a hundred pounds soaking wet with no real combat training against a man who is heralded as the greatest warrior in the entire world, who out of a desire to protect her friends, chooses to face alone. We've seen the only way that one ends.
It's obvious from her conduct in her Chapter 14 scene where she tells Cloud not to fall in love with her, and the glimpses of the OG that we experience through visions via Cloud, that Aerith has at least a partial copy of the script in her head, and her experiences in the last few chapters of the game have accelerated her on her arc to being the person who went to the Forgotten Capital to save the planet and her friends. As far as the Zack vision goes, I've stated my opinion as to why him living isn't in the cards, the presence of the time-ghosts in the flashback for continuity's sake, an excuse to show the player this scene happening in the past despite it being totally out of left field for this point in the plot. More than that though, its Aerith, not anyone else is aware of Zack Fair's final stand as we see it, knowledge that will advance her coming to terms with that and move past the lingering grief over the loss loved one she got no closure for. At no point in the course of FFVIIR do we witness anything other than information pass through time, and even then, only through the Lifestream and those who can commune with it: the TIME GHOSTS, Aerith, and Sephiroth.
Which leaves us in the exact same situation that we were in the first half of the OG. Sephiroth has all the cards, Aerith is the only person alive who can meaningfully oppose him. "But Magos," you may ask again, "if he has the script, wouldn't he just see where his failings and mistakes were and not make those again?" No. He won't. Why? Because his entire motivation through the game is protecting his pride and sense of superiority. His start of darkness begins in Nibelheim, the greatest warrior in the world, having won the war and outlived his usefullness, consigned to running cleanup operations at some broke down reactor in the middle of nowhere. A glorified janitor. That is, until he finds Gast's research, and he's not longer an obsolete tool, special. He spends the entire game assuming new, ever more grandiose titles for himself to avoid dealing with the grief of losing his position of importance until he literally tries to deify himself. "What do I have to be sad about? I'm the Chosen One." He is unwilling and unable to grow as a person. Even knowing the specific missteps he makes, his arrogance and habit of underestimating those he perceives as weaker than him remain. Now that he's manipulated our heroes into doing his dirt work and killing the TIME GHOSTS for him, his ego's likely even more inflated than it was in the OG, and it will lead him to making similar mistakes in the following entries.
But Aerith has some knowledge of these events as well, and will likely be doing her part to play the twelve-dimensional chess game she and Sephiroth now find themselves playing against each other, though the timetable has moved up a bit from when they did so in the OG. She's still the only one Sephiroth has to kill to make the plan go off without a hitch, and is still the kind of person to make a dangerous, risky play to protect her friends. It's not a matter of if, its a matter of when and how, the others left with a modified set of problems to deal with in the same way they're OG counterparts would have, and will make the same mistakes in the process. They all will.
They might have escaped the binds of predestination but none of them can escape the people they are.
I apologize for the rambling, run-on sentences. Thank you for coming to my TED talk.