I do have to wonder, if Sakurai chose an ARMS fighter to become playable, would he go with Springman (maybe with a Ribbon Girl echo fighter) as most assume? Yes, he's the Ken or Mario of ARMS, but he's also not especially interesting and the unique playstyle they could bring to Smash could pretty much be brought by any of the more memorable ARMS fighters. There's no precedent for a new series being represented by a character other than the one that's marketed as the main character, but does that mean Sakurai would turn down the likes of Helix, Master Mummy, Dr. Coyle, or even fan favorites like Twintelle or Min Min in favor of Springman? If the tradition of playable main characters representing their series were to ever be broken, I think ARMS would be the series it would happen with. As for how likely that is to happen, I'm honestly not sure, but it's something interesting to ponder.