This is my idea for what Smash would be like if it had the same alts system as NASB- every character only gets one alt, and it must be something canon (unless one does not exist). I'm also taking the extra challenge of no character swaps (no Alph, no Koopalings, does not exclude characters like alternate Zeldas) or gender swaps. I'm also skipping the Miis. This is restricted to alts that existed pre-Ultimate, too.
Wedding Mario
Casino Luigi
Vacation Peach
Hammer Slam Bowser
Hammer Mario (reskins pills into hammers)
Gymnast Rosalina
Shadow Mario
Striker Daisy
Bone Piranha Plant
Arcade DK
Rare Diddy (Rare logo on hat, no stars on shirt)
Kaptain K. Rool
Hero of the Wilds
Classic Sheik
Classic Zelda (Zelda 1 design)
Classic Link (Zelda 1 design)
Twilight Princess Ganondorf
Island Lobster Link
Fusion Suit Samus
Orange Two-Piece Samus
Meta Ridley
Classic Dark Samus
Black Yoshi
Yellow Kirby
NES Meta Knight
Shogun Dedede
N64 Fox
N64 Falco
N64 Wolf
Pikachu Libre
Shiny Jigglypuff
Spiky-Eared Pichu
Shadow Mewtwo
Squirtle Squad Shades
Shiny Ivysaur
Armored Charizard
Shiny Lucario
Ash-Greninja
Shiny Incineroar
Pajama Ness
General Lucas
Classic Captain Falcon
Climber Swap
Wedding Marth
Young Roy
Radiant Dawn Ike
Masked Lucina
Resplendent Robin
Ninja Corrin
Tokyo Mirage Sessions Chrom
Green Hair Byleth
Mr. Game & Watch Gallery
Classic Pit
Athena Armor Palutena
Classic Dark Pit
Overalls Wario
Tiger Stripe Camo Snake
Boom Sonic
Pikimar
NES ROB
Spiked Hat Villager
Winter Isabelle
Rush Coil Mega Man
Wii Fit U Trainer
Wireframe Mac
Pacster
No Gear Shulk
Pro Swimmer Pyra
Radiant Beach Mythra
Box Art Dog with Mallard Duck
Street Fighter 5 Ryu
Street Fighter 5 Ken
Advent Children Cloud
Classic Bayonetta
Splatoon 2 Inkling (uses the box art/amiibo design)
Chronicles Simon
Symphony of the Night Richter
School Joker
Cobblestone's Finest Hero
Nuts and Bolts
Garou Terry
Waitress Min Min (from her Smash trailer)
Tuxedo Steve
Tekken 7 Kazuya
Kingdom Hearts III Sora