After playing Mario and Luigi 3, Bowser needs his own game. Not half of one. One where you beat those rotten plumbers. Because, as shown in M&L3, Bowser's Kingdom is more awesome and much stronger than the Mushroom Kingdom. Bowser, though a little selfish and kind of ignorant, makes a great King because he takes shit from NOBODY and even fights in his own wars.
Daisy, Waluigi, and toad are all more minor characters than a simple goomba. They have nothing that makes them unique. They don't deserve their own game, they don't deserve to be in the next Smash bros., they only deserve a spot in the Mario Party and Mario Kart spinoffs.