Here's a thought experiment. Give every third-party franchise in Smash (with a playable character) three more playable characters. You can draw from KoF for Terry and Namco's larger arcade catalog for Pac-Man due to the fact Pac-Man and Fatal Fury's representation in Smash already draws so much from these sources.
- Big Boss (based on his appearances in Solid 3 and Peace Walker), Raiden (based on Solid 4 and Revengence), and Revolver Ocelot (skins based on his various appearances)
- Tails, Knuckles, and Shadow
- X, Zero (based on his appearance from X2 onwards), and Megaman.EXE
- Ms. Pac Man, Valkyrie, and Dig Dug
- Chun Li, Guile, and Akuma (I know, another shoto, but he's up there with Ryu for being the crossover king)
- Terra, Black Mage, and Tifa
- Jeanne, Rodin, and Father Balder
- Alucard, Soma Cruz, and Maria Renard (based on her appearance in Rondo for maximum meme power)
- Yu, Makoto, and Tatsuya
- Slime, Torneko, and Jessica Albert
- Mumbo, Gruntilda, and Klungo (for maximum meme power)
- Kyo, Iori, and Athena
- Zombie (with a new moveset based around enemy mods), Villager (with a moveset based around random Minecraft items), and the Dungeon Crawler
- Jin, Nina, and Heihachi
- Riku, Roxas, and Aqua
I'm only doing series I really know about.
![Sonic :ultsonic: :ultsonic:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
- Dr. Eggman, Tails and Shadow.
![Mega Man :ultmegaman: :ultmegaman:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
- Zero, Megaman.EXE, Tron Bonne.
![Pac-Man :ultpacman: :ultpacman:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
- Valkyrie, Dig Dug/Taizo Hori, Gilgamesh.
![Ryu :ultryu: :ultryu:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
- Chun-Li, Akuma, Sakura.
![Cloud :ultcloud: :ultcloud:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
- Tifa, Black Mage, Bartz.
![Simon Belmont :ultsimon: :ultsimon:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
- Alucard, Soma Cruz, Shanoa.
![Banjo & Kazooie :ultbanjokazooie: :ultbanjokazooie:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
- Mumbo, Gruntilda, Klungo(if it requires 3, cause otherwise, I think Mumbo and Gruntilda are enough.).
![Sora :ultsora: :ultsora:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
- Riku, Roxas, Aqua.