Let's keep Character Crossovers from other Square-Enix titles out of FFXIV.

[Denmo]

Really, Nael was not Sephiroth. I know enough about both characters to know that they were far from really being the same character. There were a few subtle likenesses, sure. But to suggest that because of those few subtle likenesses that they are the same person and therefore a crossover has already happened is kind of a terrible argument, because it's not true.

few subtle likenesses

I would hardly call it subtle. Anyone familiar with Sephiroth knows this scene.

And also:

A high ranking official goes crazy and draws upon unearthly power to unleash destruction on the planet, in the form of a giant Meteor.

Who am I describing? Sephiroth or Nael Van Darnus?

My point is, there are references to previous Final Fantasies that were woven into Eorzea's story pretty well, despite being not-so-subtle. We know it, and we love it. But now that the actual Lightning from FFXIII is coming in, OH NO, it's a terrible terrible thing! SE's a sellout and is ruining the Final Fantasy name! BURN THIS INFORMATION FROM MY VIRGIN EYES. MY IMAGE OF ALTERNATE UNIVERSES IS FOREVER SCARRED!

I'm exaggerating, but then, I think, so is this thread. Especially since you haven't seen how they'll do it yet.