The argument about Wolf getting in over Krystal is because the standard order of Smash is -
1. Protagonist
2. Sidekick
3. Villain/Anti-Hero
It happened with...
Mario, Luigi, Bowser
Pikachu, Jigglypuff, Mewtwo
Fox, Falco, Wolf
Donkey Kong, Diddy Kong, (???)
Link, Zelda, Ganondorf
So in that case, the Fox (Protagonist), then Falco (Sidekick), then Wolf (Villain) works.
And besides, Krystal is way less important than Wolf...
Sonic should stay just Sonic with a modified moveset, maybe an Angel Island Zone stage, but no new characters. Tails, Knuckles, and Shadow ATs would be good too.
Then add Megaman (Classic) with Zero AT.
No Master Chief, No Geno (prepares flameshield)...