Replace Palutena with Boo, Bowser Jr. woth Koopa Kid.
Add Dry Bones, Donkey Kong, Koopa Troopa, Shy Guy and Nabbit.
So how would this look?:
Mario
Luigi
Peach
Daisy
Yoshi
Birdo
Toad
Toadette
Wario
Waluigi
Donkey Kong
Diddy Kong
Koopa Troopa
Shy Guy
Boo
Dry Bones
Nabbit
Koopa Kid
20 characters... a bit much though.
I think 16 would work better though.
Keep discussing, I'm not to sure on this.