Oh boy... just imagining such a serious guy doing THAT is already amusing.
Who'd think Sephiroth would ever appear in a Smash game. That was like an impossible dream for many players back in the Melee days (and Brawl, to a lesser extent).
Not talking about the character's body shape or weapon. I mean, back in Melee's time there was the whole thing of "Only Nintendo characters are allowed", so something like Sephiroth (or any other third party character) was out of question. But players would still dream and talk about the characters they wanted the most, sometimes imagining their movesets and whatnot. Sephiroth was a popular choice, along with some other characters (not only from other games, but also anime, etc). I remember a lot also wanted Goku.
Maybe you didn't grow with the games or took no part in those discussions. If you want to dig up enough, just look at some of those ultra old Gamefaqs threads (the ones before the 2010s) from Melee or Brawl. There's some hilarious gold to be found.
Makes you think how good it made for Iwata not being the president anymore. I mean, we are truly sorry the way he left this world, but since he was in charge everything went wrong from a non-casual gamer perspective.