The irony is, this very idea SE has actually used in the past in FFXI as the basis for the big twist at the end of the FFXI Abyssea add on expansions - in that it was an alternate universe version of FFXI's world Vana'diel that diverged from the 'player's version of Vana'diel' at the end of the Chains of Promathia expansion, where the player's character (a god slaying adventurer just like the player's character here in FFXIV) actually died during the final battle against the Twilight God Promathia instead of coming out victorious, who then proceeded to absorb not only the player but also their entire party along with npcs such as Prishe. This resulted in Promathia changing form into Shinryu the Godwyrm, and proceeded to tear Vana'diel to pieces, Abyssea being all that was left (and even that was sliding into destruction).
Needless to say, given the fact that parallel universes and alternate realities are a big part of the FF series in general and even officially here in FFXIV as well
with the whole 'Source divided into fourteen 'Reflections' and the Warriors of Darkness being Ascian-corrupted parallel-world versions of the Warriors of Light,
it would not surprise me if SE does actually use this concept in the future, presenting an alternate Hydaelyn where the player's character met their end for whatever reason, and the implications this has on Hydaelyn at large and Eorzea in particular.