I think this is one of the known elements of fiction. "What if this event didn't happen this way?"
SE has already given us this scenario at least twice. The original Dynamis zones could be considered the "What If?" of the Allied Forces losing the Crystal War, and Wings of the Goddess gave us a little bit more on that.
Abyssea presents us with a scenario focused on what would happen if *we* did not win the final battle against Promathia.
But what about other scenarios?
What would have happened had we lost the fight in Apocalypse Nigh? What about the fight against Alexander? Besides the Crystal War never ending, what about Lady Lilith's dimension? We're told what would happen, but how much more is there? Before Abyssea, could you imagine that exactly what happened in Abyssea would have happened if we lost against Promathia?
How about the three story add-ons? What would've happened if we lost against the Seed Crystal? Riko Kupenreich? The Shantottos?
I doubt we'll ever truly know. I'm just curious how the world would've turned out. Maybe give the writers some new storyline ideas. *coughhinthintcough*
First person to say "If you lose the fight, you just get kicked out of the BCNM" gets stabbed in the eye with a rusty spork. =D
First person to say "SE doesn't care about FFXI anymore so don't expect any of those answers" gets their uvula tied to an opo-opo. =D