The Buster Sword as seen in AC is actually hollow. In it, Cloud is hiding a forgery of
The Fallen Madonna With the Big Boobies by Van Clomp.
During the credits, Cloud will pencil himself in a vacation day from his delivery service, to be taken whenever he chooses. Tifa will find it very sweet, until he informs her its actually for the next time Sephiroth inevitably finds a way back from the dead. She will then punch the shit out of him.
And Usher, type up that 10-2 idea. I at the least would be curious.
OK, since you asked... Although, I now realise it's been years since I first came up with it, and I can't remember it fully.
So, here's a rough guideline version. I first came up with it in a fit of "wtf?" at Nomura's comment that FFX/FFX-2 was the past of FFVII. It's pretty much pure crack. Anyway...
~~~~~
The events of FFVI
Magic ‘dies’ from the world. The old age of the world ends.
Terra has a son, possibly with Edgar. The child is named Heine.
The heroes of FFVI eventually die out, due to age, natural causes, etc. Heine discovers he retains a small amount of the magic that once encircled the world. Eventually, he develops an obsession over his power, and attempts to enslave the world.
Heine lives for centuries, unnaturally prolonging his life. He takes many ‘brides’ during this time, but finds he can only sire daughters. These daughters will in time become known as sorceresses.
The people rise up against Heine, only to find they have been attacking a decoy. Heine disappears, never to be heard from again. Over the years, Heine’s name is incorrectly transliterated into the form “Hyne”.
The people who rose against Heine found the civilisation that encompasses the globe, which will one day called the Centra. Centuries later, the Centra civilisation seemingly vanishes over night.
The first Guardian Force is discovered. Some GFs take forms similar to those once owned by the Esper civilisation. No-one remembers the Espers enough to notice the similarities. The GF Odin takes residence in the most impressive of the ruins left behind by the Centra.
The Shumi are discovered in the far north.
The Ester, an until now minor civilisation, is taken over by a sorceress. As it comes time for the sorceress to die, she passes her powers to a successor, who then becomes commander of Ester. This continues until the reign of Adell, who is ‘outwitted’ by a former Galbadian soldier called Laguna Loire and his colleagues.
During the reign of the sorceresses, a form of matter/energy manipulation is pioneered. It is finally perfected for use with a Guardian Force by one Dr Odine, who names it para-magic. Para-magic becomes widespread.
The events of FFVIII
The Ester government produce several transport vehicles, all based around a similar design (as seen in the shuttle Ragnarok).
Eons pass. A meteor fragment impacts, and emit’s a strange force that destroys the Guardian Forces. It also has another effect. The people of Ester, more and more enamoured with technology, start to evolve differently from the rest of humanity, the only tell-tale sign of their difference being their spiral pupils. They begin calling themselves the Al Bhed.
It also effects the life-cycle of the Shumi and their Moomba relatives. The Shumi slowly become more humanoid, no longer metamorphosing during their own lifetimes. Likewise, the Moombas slowly become more humanoid, developing impressive horns and rudimentary speech along the way. The become the Guado and Ronso, respectively.
The Al Bhed are driven out of Ester by an invading group of humans, who rename it “Zanarkand”.
The first Fayth is founded in Beville. It takes the form of the dragon king, Bahamut. A few ponder over the similarities, but dismiss it as an embodiment of an old fable.
The machina war between Zanarkand and Beville
Time passes…
The events of FFX/FFX-2
The Al Bhed uncover an airship of Ester design, which they dub “Celsius”. This is procured by an Al Bhed called Brother. The Al Bhed later uncover an experimental piece of magitek armour from eons past. This is dubbed the “Machina Maw”, before being procured by Brother’s sister, Rikku. (The Al Bhed are not amused.)
An Al Bhed called Shinra sees the potential in drawing energy from the spirits of the deceased on the Farplane.
The Al Bhed are gradually re-absorbed into the main human genome after centuries of inter-marriages.
The Guado further evolve, renaming themselves the Cetra (any relationship to the vanished Centra civilisation is unknown).
The Ronso, however, seemingly devolve, losing the ability to walk bipedal and becoming quadrupeds. They also lose their horns. However, they become far more genteel in their speech patterns.
JENOVA crashes to the Planet
Materia is discovered, a physical form of the Planet’s knowledge. Summons are also found, once again some taking forms used by the Espers, GFs and Fayths.
Time passes…
The events of FFVII
Further into the future…
The Planet hits meltdown. The few survivors go into a form of suspended animation. The Planet becomes known as Terra.
The events of FFIX
Hopefully they never try to do anything like that for real. The Spira-to-Gaia connection made sense, but the novelty is cool only as long as it remains a novelty.
It definitely wouldn't be a few hundred years, though, as Nanaki states in game that he expects to live for five hundred years (which we know from the ending of VII and beginning of AC, he does). Also, please note that Nanaki's species is the final form of the evolution - although they have devolved physically, their mental ability is better than most humans.
