I have some newcomer ideas inspired by older and newer Smash games (and more):
Daisy (Super Mario)
Koopa Troopa (Super Mario)
Mona (WarioWare)
Zelda (The Legend of Zelda)
Sheik (The Legend of Zelda)
Tetra (The Legend of Zelda)
King Dedede (Kirby)
Bandana Waddle Dee (Kirby)
Knuckle Joe (Kirby)
Bonkers (Kirby)
Sceptile (Pokemon)
Zoroark (Pokemon)
Greninja (Pokemon)
Incineroar (Pokemon)
Sylux (Metroid)
Wolf (Star Fox)
Leon (Star Fox)
Panther (Star Fox)
Ninten (EarthBound/Mother)
Black Shadow (F-Zero)
Roy (Fire Emblem)
Ayumi (Famicom Detective Club)
Amy (Sonic)
Bass (Mega Man)
Akuma (Street Fighter)
Taizo (Dig Dug)
Prince (Katamari Damacy)
Renamon (Digimon)
Cloud (Final Fantasy)
Sephiroth (Final Fantasy)
Risky (Shantae)
Piccolo (Dragon Ball Z)
MX (Mario '85)