I've written down some reasoning for each of my choices here. Please, take a look.

* Prince of Sable is just a little scrunkly. He'd be a really cool transformation fighter with his frog and snake forms. His game is niche, but has indirectly inspired a lot of RPGs today through its influence in Link's Awakening.
* Tom Nook would make for a cool fighter with a potential point buy gimmick based around buying special moves.
* Wart could be a floatier echo of Bowser, plus represent a pretty neat game (and rep >!the new movie!<).
* You've got to admit the eShop music is good, and remixes of it would go incredibly hard. I'd take any Wii-era hardware rep who'd get that music in, not just the bag.
* Monokuma!!!! I always thought it was a missed opportunity to not have a Danganronpa character in Smash *Ultimate*, but I feel like with the relevance the franchise has had in recent years, there really isn't any excuse for the next game.
* Hoopa would be a shifty little trickster who uses teleportation and projectiles to its advantage. Plus, you could definitely add little cameos of other Legendary Pokemon through attacks coming from its hoops.
* The debate on whether Segata Sanshiro counts as a game character or not is kind of controversial when he's brought up, but I personally think that even if he isn't, Smash is a celebration of gaming in general, which goes much beyond just the games themselves and could get in on something similar to ROB logic.
* Not too deep of a cut compared to some other reps, and it's definitely too late to see this in Smash, but I'd honestly take any character from Skylanders on the roster.
* Mr Grizz is one of the few Splatoon reps who wouldn't be just a semiclone of Inkling, which makes him a good Smash candidate in my eyes.
* What more is there to say about Sonic? Honestly, he needs a rework at least and a new fighter (or two) at most.
* Might be too redundant having both Monokuma and Takumi in Smash at once, but I'd also really love to see The Hundred Line get some more recognition, considering how ambitious of a project it was (and how it got snubbed at The Game Awards I mean what). Plus, there's some moveset potential to be had with the whole >!timeline thing!< the game has going on.
* Despite being a joke rep, Harold from RPG Maker reps not just games made with RPG Maker, but game-building software in general. His moveset might not be too unique unless you get meta with it, but his presence would be so funny to me.
* I grew up playing Where's My Water, so this one was an easy pick.
* Yeah, I don't really want Waluigi. He's just a clone of a clone, and only has fan recognition behind him, as opposed to other commonly requested characters who are a lot more relevant and important to gaming.
* A chakram user would go so hard, hence putting Mio in this slot.
* Wait, don't go, I'm not an NPC! Tales of Symphonia on the Gamecube was my first Tales game, so I have a soft spot for it, and because of it, RPGs in general.
* Astro Bot was the most fun I've had with a game in literal years and honestly revitalised my fondness for the PlayStation, so I'd love to see him in Smash one day.
* And finally, Wingo's my guy. He's just my little bird man. If we can't have him in Mario Kart, I'm gonna go higher and ~~piss on the moon~~ get him into Smash. Nothing more to say.

That one Smash wishlist trend but it's objectively weird