Also, for the sake of conversation, here's what I've narrowed down as the 36 "essentials" for Smash.
Some notes, characters like Min Min stick around since I feel that major first party IPs should never be cut outright, and Smash has always made it a point to maintain those when possible too. In general I think it's harder to see Smash 4 / Ultimate characters as "mainstays" yet in general so it's difficult to call whether or not they'd be in any danger moving forward. But I don't see many of them leaving, as either Nintendo icons in their own right or longstanding heavily requested characters from major series.
I left out
only because I feel Isabelle has effectively become the face of the series and can do most of the same stuff, on top of being a defined character rather than an avatar. In reality they'll probably both return, but when keeping it concise I'd prioritize her in the end.
Miis would probably be there too, just feel it's easier not to have them there when trying to narrow things down to a specific amount. Although Nintendo doesn't use Miis quite as much as they used to either, so it may not be a priority depending on what the future holds.
Also I suppose
should probably be here too, Pokemon Trainer was just expendable because it's a full three characters to develop. If Smash 4 is any indication, Charizard is clearly significant enough to keep with or without his Trainer.
Villager is the main playable character on Animal Crossing and Isabelle was only addable because he existed. She had no clear moveset without an easy base. She couldn't be more than a semi-clone and was considered for an Echo slot. But she wasn't there just because they wanted the face, she's there because she's a massively popular Nintendo All-Star and easy to add.
It's like cutting Ryu for Ken, frankly. Villager is a mascot to Animal Crossing too and has a very clear point behind it. They represent the core gameplay. Isabelle is the major favorite semi-clone who is there because AC deserves a lot of content with how big it is as an overall successful series. It doesn't have nearly as much as others game-wise, but it's still big and important.
No base character has ever been removed for their clone, and it's massively unrealistic here. It won't happen(Marvel VS Capcom pissed off multiple people for pulling that crap, removing tons of notable characters and using the ****ty excuse of gameplay functions. Crossovers strictly rely on characters, not movesets, as their bread and butter). Isabelle, for that matter, is lucky that she had someone to base off of, otherwise she'd be way harder to add since she had no clear moveset too. She wasn't designed to be "a representation of AC's gameplay" either. She was designed to be a cutesy take on Villager due to her own mannerisms, and once again, was considered for an Echo, which we know all of them are cases of "they're hard to add on their own merits alone". She didn't lack merits, but let's be real, she'd need a way different moveset to represent her if she wasn't a semi-clone. Work projects are a big thing for her, and a lot harder to do since she'd be completely unique. Ultimate was rushed, meaning that the fact she was a semi-clone is what gave them enough time to get her in. If that wasn't the case, either we'd have other characters cut(unique ones. But who, I dunno. That's the problem. None sound like they would've been cut. Maybe Incineroar wouldn't have gotten made at best?), Villager would've been first anyway(since they're the most important character for the franchise's core gameplay representation, bar none), or they would've made her DLC due to not enough time to actually make her playable.
PT should always be in, but he has a gameplay reason to be cut, like last time. That's at least justified. That, and he's not the first actual Pokemon character. The one time there was a consideration was Ness changed out for Mother 64's protagonist, but this was also during Melee, where characters weren't established as mucho important yet. Also, consider this factor; Tom Nook was not the one Sakurai wanted to add in Brawl. Villager was. Being the face clearly wasn't that important over the actual core gameplay representative. Villager was always going to be first, and they're always going to be the main representative. It's pretty clear what Sakurai goes for in these cases. This is literally the same reason Hero was gotten over Slime, the actual face. The player character is mucho important, far more than the mascot, when it comes to representing how a game plays. That's important to the crossover aspect too. Slime was only the second choice for him if and only if he couldn't get Hero(since the mascot makes sense). Pikachu, for that matter, is the one exception simply because PT was impossible to add due to a very limited amount of potential gameplay stuff. They weren't even knowingly considered till Brawl for that reason(rumors at most, like in Melee). That, and we know Pokemon is unique by being anime driven in choices at times(not all the time, contrary to popular belief. Mewtwo, Jigglypuff, Pikachu, and Lucario, and you could say that with Charizard to some degree, are the only 5 that were due to anime influence in itself. Pichu almost fits, but it was the mascot of Gen II for Baby Pokemon and already had a movie, but, you know, easy clone. It made sense at the time, even if there was a movie starring it. Incineroar was due to the Wrestling factor and a slot set aside. Greninja was chosen even before being in the anime, though had concept art related to it, like Incineroar. Ivysaur is just a lucky lastover bit. Squirtle was Blastoise at first, but changed to for gameplay balance reasons. PT using Red's design is however meaningful, since it's the face of Trainers for the franchise, enough to be confused with Ash by fans, but also actually is compared to Ash, so in a sense could be called semi-related to the anime for which particular design is chosen. But that I'd chalk up to a coincidence either way).
I can understand most of the third party picks, but Steve is massively safe due to being a gaming icon. So that should be added back in along with Villager for a more realistic roster.