if Waluigi gets in, I think his trailer would HAVE to be a bait-and-switch, not an in-universe one like K. Rool's, but a convincing out-universe bait-and-switch among the lines of Lucina and Robin's trailer - I personally would make the viewers think there's gonna be an FE character, have Waluigi take the spot and give the "hoes mad" crowd a good wallop of karma.
YOU HAD ME AT HELLO