InB4thatwasbetweengameswhichmakesitdifferentbecauseittakesSakuraiaminimumofthreeyearstochangehismindbecausereasons
Turning an AT/Pokeball/Boss/whatever into a playable character is much easier then making a character from scratch. You already have existing assets in the game, and it would be stupidly easy to remove said character from whatever role they had previously. (Functionality to do that is even built into the game) Say Bandanna Dee gets into the game, I guarantee he'd be built off of the existing Waddle Dee model in Smash Run, since that model is already rigged and has several animations already done. If Captain Toad made it in, they'd use the existing Toad model as a base and build off that.
Let's say Waluigi gets a decent amounts of votes on the Smash Ballot. Is Sakurai just going to completely ignore that because he's already an assist tropohy,
with a fully rigged model and several animations already in the game?
Let's use Takamaru as another example, Sakurai said he didn't make the final roster because he wasn't popular enough worldwide. But say Takamaru does decently well on the ballot, or that a new Takamaru game is made, is he going to make a character off the existing assets he already has, or is he not going too because some people on a forum said there's no way he could?
Say Ridley gets a redesign in the next Metroid that would work in Smash, one that Sakurai thinks could work. Does he ignore a highly requested character that people have wanted for over a decade because of a made up rule?
Really, the only reason it's unlikely too get an AT/Pokeball/Boss/whatever is because people
HAVE the false notion that they can't be done. Which is silly, but it will decrease the amount of votes they get on the ballot.