On a side note, something interesting I realized when reading through Sakurai's article about the DLC in Smash 4 in 2016....
http://www.sourcegaming.info/2016/02/21/nintendodream3/
—Geno is also popular with our readers as well. The Flying Men from Mother come from an even older game than Geno, and the only available assets are sprites. How did you make them into a costume?
Sakurai: On the 3DS version, the Flying Men appear as sprites, but we actually made a 3D version of them. After inspecting the models, we concluded that the 2D models looked better and that’s how things ended up working out. Because of that, we had a 3D model that had actually passed inspection. So we modified that to make it a Mii Costume. On the other hand, not having that pre-made 3D model doesn’t mean that we wouldn’t have made these Mii Costumes.
This is the part on the Flying Man Mii costume. Sakurai made the FM Mii costume because he had a 3D model of him already available. He wanted to make the FM stage hazard on the Magicant stage in 3D, but couldn't, instead making it the same 16-bit FM from Earthbound. Take a close look at the last sentence:
"On the other hand,
not having that pre-made 3D model doesn’t mean that we wouldn’t have made these Mii Costumes."
Sakurai would have made the Mii costume even if he didn't have a 3D model. Sakurai wanted to make something for the Mother series. A new one definitely has to be considered at the very least. And like
The Anigriffin
pointed out in her powerpoint, the FM spirit is from Mother 1, meaning that if it is a hint to the new character, it will be from Mother 1