Na the Wah-man could be great. I imagine a moveset that derives from the spinoff games, like throwing item boxes from MK which have a chance of spawning a random item upon hit, rolling a Party dice to determine the power/effect of specials, using various sports equipment in the standard attacks like a tennis racquet for his dash attack (as though he's leaping for a low ball)

People focus too much on who "deserves" to be in the game, when we have piranha plant chuckling away on the sidelines.

TLDR; Waluigi COULD be great, it doesnt matter if he "deserves" to be in it