Newcomers
1. Dixie Kong
2. Chorus Kids
3. Inkling
New Clones
4. Toon Zelda (small, fast Zelda)
5. Plusle & Minun (two Pikachu attacking one after the other)
6. Medusa (slower, stronger Palutena with darkness effects) [I'd rather have Lucas, but I'm sticking to your rules]
Veterans
7. Ice Climbers
8. Mewtwo
9. Wolf
It's pretty tough coming up with new clones that make sense. Medusa barely works, and I'd replace Palutena's shield bash attacks with claw swipes -- Ganondorf had his own jab and forward air in Melee, so why not?