And then, that beautiful music, the melody of Terra's theme and what is de facto theme of the game, by having it played as the world map theme. It's a remarkable opening.
And it's precisely what gives the strongest link between players and the Magitek Armor. It's the moment we have the best perspective of it trudging across the frozen white wastelands.
So yes, it fits - The best Magitek walk ever is done using that specific song.
And I agree that the Magitek Factory would be a nice choice as well, from another perspective: it fits by being the theme of that thing's "home", their birthplace. We never used them while it plays, but we can imagine it fits. How? The atmosphere it gives.
So, it's a /signed for me too, as useless as it may be.
And by the way, you Rachel analogy is... not good. Rachel wasn't the only dramatic death in FFVI. Forever Rachel reflects one thing. The Opening theme actually reflects the game as a whole. It connects the story.