TL;DR My apologies for this post being more mean-spirited and dystopic than I originally wanted it to be. This was just supposed to be a joke speculation post, but instead it quickly grew into an unfunny-satire-structured indictment of Nintendo's 10+ years of resting on its laurels and falling asleep at the wheel.
Every Super Smash Bros. game would have a story mode, and that story mode would always go in the same order of "
grass word, desert world, water world, jungle world, ice world, fire world." As a result, various big name modes (Adventure Mode, Subspace Emisarry, Smash Run, and Smash Tour) would never exist.
*"Ding Dong The Witch is Dead" starts playing as people celebrate Smash Tour never existing*
The games would play much more like a traditional fighter, but items and the ability to have four people playing at once would still be a thing.
Also we'd have gotten all the mario and zelda reps we currently have a lot sooner. Bowser, Peach, Ganondorf and Zelda in Smash 64 (with Luigi being a starter character instead of unlockable). Wario, Dr. Mario, Bowser Jr., Young Link, Toon Link and Sheik in Melee. Rosalina, Daisy, King Boo, Impa, Midna and Wolf-Link in Brawl. Waluigi, Toad, Shy Guy, Lana, Tingle and Ghirahim in Smash 4. and then finally Birdo and the dark souls dragon from Odyssey along with Linkle and a BOTW rep in Ultimate. As a result, we would never get characters like
or
.
Characters like
,
,
and
would all be added one game earlier, but would be reluctant additions that would be permanently cut the very next game.
Fire Emblem and Pokemon would both be much more toned down in their representations, but would still have the fundamental issue that both franchise's reps have (Fire Emblem would still get nothing but Sword Lords, Pokemon would still be an OCD-inducing nightmare that's too reliant on Gen 1. Instead of
, we'd have
, Butterfree but not Beedrill, Pidgey/Ratata/Magikarp as a tag team, only one of the Gen 1 Eeveelutions and neither of the others, and then Moltres but not the other two elemental birds.
would be a hard "maybe"). Captain Falcon and Ness would still be in because "lol tradition," but Miyamoto would do everything in his power to keep them as underrepresented as possible. Which means no
and instead of getting new stages almost every game for the two franchises like we have been, it'd just be Port Town and Onett (that's right, the two boring crap stages. no Big Blue and no Fourside) and no other stages repping those games.
Kirby and Metroid start with two reps, which they would keep for the entire franchise history:
and
respectively. Star Fox would be exactly the same as it is, except Wolf isn't cut from Smash 4, and Slippy would be a newcomer for Smash 4.
There would be no third-party characters whatsoever, and no Xenoblade reps either.
64 would be considered the best one. It'd have a much larger roster, and the physics would've aged much more gracefully, like how Super Mario 64 allegedly did. Melee would be the controversial one. While it might have still been the competitive juggarnaut as the version we got allegedly is, it would be doing so under a much different context. Some would worry that the series was getting stale already. Brawl wouldn't have the floatiness, tripping, or anything else the melee fans don't like about it, but it would be much more authoritarian in making you use the motion controls. It would be universally reviled by the FGC and the fanbase as casual trash, and the critics and casual players would call it derivative and boring. Smash 4, assuming the franchise would still be limping along at this point and not outright dead from Miyamoto's refusal to do anything interesting with the games, would be the final nail in the coffin. Miyamoto's habits would reach critical mass, with almost everyone loathing it for being the New Super Mario Bros 2 of the series. Ultimate would be the point where Miyamoto isn't allowed anywhere near the project, just like with Mario Odyssey and BOTW. It would be praised for breathing new life into the series, but would ultimately be forgotten after a couple of years.
In short, Miyamoto-- as good as he is with the Mario games --would've been a terrible pick for directing smash, as unlike Mario, Smash is a much more delicate series that wouldn't have survived the Wii and Wii U eras had it not been for Sakurai's weirdness.
But hey, on the bright side, this is a thread about Miyamoto directing the Smash games. At least it's not Sakamoto we're talking about, or this post would be nothing but catastrophizing on my end.