Maybe they're looking at this the wrong way? Maybe Mario could consider her female form as her "natural" state, and treat her male Bowser form as this transformed "beast mode" when shit goes down. Thus furthering the badass appeal of Bowsette.
(Great. Now I'm imagining her getting all ghetto and taking her crown off like a woman taking off her earrings)

Who wouldn't want a smoking hot wife that can decimate monsters and glass large sections of dessert on a whim?

That's a pretty big Bowser too. I'd say Galaxy size? Looks bigger than he did in Odyssey.