Nice to see that the fan theory regarding OMG has panned out. Always thought it was a waste for Omega to have its epiphany only to die moments after. I have to admit, though, that this story focuses on my least favorite part of the ShB plotline: the whole "send someone to the past to prevent a dark future" thing. I don't like the idea that, no matter how bad things get, we always have time travel as a back-up plan. The fact that all kinds of unlikely things had to come together to make it possible doesn't matter; the fact that it's possible at all cheapens our accomplishments, in my mind. It also tends to ignore the fact that the BAD GUYS could use this kind of cheap trick, as well - and being immortal, they have plenty of time to figure out how to do it WITHOUT the handful of MacGuffins the heroes had to cobble together to get the job done.
It also leaves a bad taste in my mouth that Cid would just give up. "Nup, things are just too awful. Time travel is the only option!" This isn't the first Calamity the world has gone through, and even if it's the worst of them, it seems too early to assume that it's impossible to recover. The time travel option should have been, at most, a side project, while they focused on the true task of guiding what they can of civilization through the Umbral Era. Of course, WE know that the Ascians plan to revive Zodiark has succeeded, and everyone will eventually be doomed no matter what they do, but THEY didn't know that - all they could see is that the world was a crapsack. The world has crawled back from the brink seven times previously; why were they so sure that, nope, wasn't gonna work this time?
And maybe I'm a cold-hearted curmudgeon, but the efforts of the story to tug at my heartstrings fell flat. Probably a large part of that is because this is all an erased timeline anyway, so nothing that happens in it really matters.
Well... Not necessarily. We don't know the time scale that Zodiark works at. Stopping the Calamity? Healing the world? We're never given any estimate of how long those things took to do, and the Ancients are immortal beings. If he were to be revived right now - well, Hydaelyn left him an AWFULLY big mess to clean up. I could easily see the Big Z spending a few hundred of years cleaning up all those Shards while the folks on the Source stew in their squalor and wipe themselves out. Just because we don't see any evidence of Zodiark for a full two hundred years does not mean that he's not awake and active.
Basically, just because Zodiark isn't doing stuff on the Source, right now, doesn't mean that he's not out there doing his thing. Powerful as he might be, we don't know that Zodiark can simply snap his fingers and do anything he wants in an instant. Additionally, he wouldn't be at full power, with only eight-fourteenths of him rejoined. It could be that eight was enough to free him, but not fully restore him - eight was enough to give him enough agency to finish the job himself, but it doesn't have to be a quick process.