I also want to add that Wario is more then big enough to warrant at least one more rep, after all, the series' legacy consists of:
-8 Platformers
-10 WarioWare titles
-DSi Ware standalone versions of Paperplane and Pyoro
-Wario Blast
-Mario & Wario and Wario's Woods, which are essentially Wario's equivalent of the Arcade DK era
Outside of it's own games it also has:
-The Mario spin offs, which feature a very constant string of Wario series content,
including appearences and references to Wario series characters
-The Rhythm Heaves series, which has at least one WarioWare guest appearence each game and in the case of Megamix,
two whole challenge sets featuring Ware's main cast.
-
Picross NP Vol.7, which features a Wario Land 2 set of puzzles
-Starfy 3, which features Wario in a heavily Wario Land based guest role
-Wario's Woods is featured in NES Remix 2
-The Badge Arcade, which featured Ashley as one of it's mascots, as well as a WarioWare set and a WarioWare x Majora's Mask set
-And Smash itself, which treats Wario as it's own franchise and much like with Donkey Kong, references his relationship with the Mario series, without lumping them together, unlike Yoshi for instance.
There is also just how Wario's appearences outside of his home series are all heavily influenced by his own series.
His greed, strenght, love for garlic, association with bombs, the Shoulder Charge, his Plane, Bike and Car, his biker persona, Diamond City and even design tweaks like the short sleeves, are all elements that come from his own series, with his rivalry with Mario and his spin off partner Waluigi being the only Mario series elements that are really relevant to him these days.
Wario is a big series and I sincerely believe that the only reason people don't see it as more of a no-brainer for a new rep is that Wario fans online tend to be pretty quiet for the most part, but I think it's well overdue for more love in Smash and Kat & Ana, being the most recurring Wario characters period, would be a fantastic choice to fill that gap.