In the original game Swallow fury is not an aerial move, I know this. But the logic here is to only use one part of this move, and this part used is an aerial part. And in the original game, it is also an aerial part. So I see no problem with this move as this is not the entire Swallow Fury that is used for B special in air.
About captain Falcon, I know, but this is the same here, the part Fury is a direct reference to Blade Fury, you can't deny that, so it is the exact same move, but with a different animation, like Captain's falcon kick. Barbatos said he didn't want the entire move to be used in air, and I understand him, because it would be completely unrealist and a fault if we look at Emil's characteristics. But as Swallow Fury has a part that is in air, and this part is an altered version of Blade Fury, we can use it. I definitely support this altered arte, which should be called Blade Fury, in ground and in air.
And honestly about the choice of Emil or Ratatosk, even if they are the same person, I definitely think it should be Emil with red eyes, so Ratatosk if I follow your logic. You're right, it has a major importance for the final smash. The entry animation, the choice is less important, even if it has incidence. But, why should we choose Emil with red eyes? If we play the game, it is definitely the best option. Those who have played the game knows that Red eyed Emil is our best option, not only for the final smash, but when it is about fighting, it is much better to have red Eyed Emil, as in the game when you fight, most of the time, you're Red eyed Emil. (I don't think it is a secret for anyone.) Besides, and this only my opinion, as we're talking about fighting in Ssbb, which is rather nervous especially when there are 4 players, the voice of Red eyed Emil (and I'm talking about his true voice, his original voice, so in japanese), would be better for a fight, because this voice express much more the fact that we're in a fight.