Yes. Yes I would.
We already have 1 and 2, and 4 exists briefly as one of his taunts. Plus your suggestions of one alternate costume for Mario, Luigi and Wario are simply "normal w/o cap". Not only does that sound like a very boring "costume" for three whole characters, but it'd be much harder to distinguish in actual Brawls as opposed to different color schemes, which are what these different colors are all about.
So to answer the question you keep on asking, yes: I prefer Red, Blue, Green, Yellow, Brown and Fire Mario over regular Mario, fire Mario, Dr. Mario and capless Mario. I prefer Green, Pink, Blue, Orange, Waluigi Purple, and Fire Luigi to regular Luigi, fire Luigi, capless Luigi and the (admittedly awesome) Mr. L. I'd prefer Wario's 12 color variations to plain Wario, WarioWare Wario, Wario without cap, and... err... Dr. Wario.
And even without your suggested format, we have plenty of canon alternate costumes... Fire Mario, Fire Luigi, Overalls Wario, Daisy, Dark Link, OoT Zelda, original brown-hair Toon Link, Four Swords Toon Links (green, purple, red and blue), Dark Toon Link, Phazon Suit Samus, SNES-design ROB, original white Kirby, Adventures Fox(?), Blood Falcon (different logo and all!), Pikachu w/Ash's cap, various other Pokemon Trainer's hats on Pikachu and Jigglypuff, and Claus-style Lucas.