I think they should stick with Mario, Luigi, Peach, Daisy, Wario, Waluigi, Yoshi, Birdo, Toad, Toadette, Boo, Dry Bones, Hammer Bro, Blooper.
Newcomers/Unlockables Baby M, Baby L, Petty Piranha, Diddy kong, Funky kong, koopa, shy guy, toadsworth maybe bowser after you beat the story line.
Dk...