-Lightweights
Toad (w/Pit Crew, Party Time outfits)
Toadette
Koopa Troopa (w/Freerunning outfit)
Dry Bones
Shy Guy (w/Pastry Chef Outfit) - Dons the General Guy outfit and fires off multiple Bullet Bills that target an enemy. They are slow and cause a small explosion.
Baby Mario - Super Baby Mario. Gains invincibility and speed, but nothing else.
Baby Luigi
Lakitu -Spiny Attack. He puts on a Spiny Hat similar to the ones in Smash, and throws a few out. They'll move around slowly, and faster towards other combatants. They won't move towards Lakitu, but he's not immune.
Larry
Lemmy
Wendy
Kamek
Blooper
E. Gadd
Nabbit
Cappy
-Middleweights
Mario (w/Fire, Ice, Doctor, Builder, Wedding, Musician, Hakama, Santa, Happi, Classic outfits) -Fire Mario instead, and maybe remove Ice Mario or make it go a darker blue? Allows him to shoot a huge fireball, or smaller ones by mashing the Item Button.
Luigi (w/Penguin, Classic outfits) - Cape Luigi. He'll go a bit faster, but also can use the item button to spin around, deflecting some obstacles. You cannot use his drift.
Peach (w/Kimono, Vacation, Wintertime outfits)
Daisy (w/Holiday Cheer outfit)
Yoshi (w/Reindeer, Egg Hunt outfits)
Birdo
Diddy Kong - Rocketbarrel. Basically in drift mode, and can fire straight in front of him with two shots. This lasts very shortly compared to your general power-up due to having no real downsides.
Bowser Jr.
Iggy
Ludwig
Pauline (w/Party Time outfit)
Hammer Bro (w/Boomerang, Fire, and Ice colors)
Captain Toad - Takes off his backpack, and speeds forward very fast. Is extremely hard to control, almost like a bullet bill. Lasts fairly long, but he loses his acceleration entirely after it's done and goes very very slow in return, like the Heavyweight acceleration speed.
Dixie Kong
Cranky Kong
Captain Syrup
-Heavyweights
Donkey Kong - Barrel Mayhem. He throws out a bunch of Barrels in front and back of him. These do not hurt him. He has a retro-like coloring like the original DK Arcade game during this, including some pixels.
Wario (w/Hiker outfit) - ...Was this supposed to be Biker outfit?
Waluigi (w/Bus Driver outfit)
Bowser (w/Dry Bowser Costume) -Big Steely. He brings this out and throws it into the the actual course. It always stays on course like a bowling ball, going forward for a bit(think versions of the Blue Shells that stay in the middle of the road). This cannot hurt him either. Once it hits a maximum of 2 or goes for about a few miles(or so. I never could determine that well), it disappears.
Rosalina (w/Halloween, Aurora Costume)
King Boo (w/Luigi’s Mansion Costume)
Petey Piranha
Funky Kong
Wiggler
Roy
Morton
King Bob-omb
Boom Boom
Pom Pom
Chargin’ Chuck
King K. Rool
Others-
Lightweight
Baby Peach
Monty Mole
Virus
Mini Mario
Polterpup
Ashley
Isabelle
Kirby
Olimar
Chibi-Robo
Middleweight
Donkey Kong Jr.
Peachette
Broozer
Chimpy
Topper
Hariet
Mona
Inkling
Fox
Sonic - Super Sonic. This is mostly similar to Captain Toad, but instead he doesn't move as high forward as he moves to the side a lot quicker. Much harder to control. Anyone he runs into is hit hard like a Blue Shell. But again, once done, his acceleration tanks.
Pac-Man
Heavyweight
Metal Mario(only put here since they're on the maybe list) - Flying Metal Mario. Moves a lot faster, and the opponent cannot use the drift mechanic against them. Does not gain invincibility frames. Acceleration remains the same.
Lubba
Spewart
Rango
Jimmy T
Link
Samus
Captain Falcon - Falcon Punch. He juts forward with a blow akin to throwing a Bob-omb, knocking out anyone along the way.
Mega Man - Hyper MegaMan. A callback from Marvel VS Capcom. Being this is a crossover game, sure, why not. He fires a lot of missiles and then a laser, while also moving slower. These do not target outright(but do go forward like throwing a banana forward). The missiles do cause a decent-sized explosion, of which he will not be hit if he comes nearby at the time. The explosions are not that huge either.
Other than lacking Villager, who has no business being cut, I don't have a lot of ideas.