I think it's funny how a character can be disqualified for being "not for good boys and girls" when we still have the likes of Bayonetta, Zero Suit and Snake in the game. So guns and partial nudity apparently aren't enough to get banned, but because Sakurai actually said there was a limit, we have to accept that some characters are just too racy to get in.
But none of those characters are inherently sexual. Sure, they're physically fit and people are prone to finding them sexually attractive as a result, but their outfits and behavior in and of themselves are not what would be considered overtly sexual content. In terms of outfits, while ZSS and Snake's skintight suits leave little to the imagination, none of them show a lick of skin, nor are the outfits themselves inherently sexual. After all, a sneaking suit is just a piece of fabric.
The same goes for Bayonetta's "clothes", and while she has a tendency of stripping down to reveal her bare bits in her games, it's not required of her to do so in order to use her powers. Simply removing a bit of cloth from her extremities would be enough to pass censors whilst still stayting true to the character. Hell, you could even surmise a lore reason as to why that's the case. Perhaps she holds back during battles in Smash so as to give her foes a sporting chance? I mean sure, Pit's an angel, but he's nowhere near as monsterous and powerful as the angels Bayo typically trounces, and thus wouldn't require as much effort to sufficiently combat.
In terms of personality, Samus and Snake are very straight-laced, no-nonsense combatants. Aside from a single line from ZSS that could be seen as lewd, there's nothing between the two of them who While Bayonetta is a lot more flirtatious with a bit of bad language thrown in for good measure, her lackadaisical jibes in Smash are rarely related to anything sexual, and her speech is entirely PG.
As for the gun argument, that's always been a fan rule rather than anything concrete. To my knowledge Sakurai has never gone of record stating that real-to-life guns were ever off the table for Smash, and their not being included has always just been a coincidence. Besides, Smash is rated E-10+ after all, and E-10+ games allow for "more cartoon, fantasy or mild violence, mild language, and/or minimal suggestive themes.", so shooting Mario with a realistic gun to have to comically fly off into the distance would fit.
Now let's take a moment to contrast this to Mai. Mai's base outfit is incredibly revealing, and while she does sometimes wear more conservative clothing, even those outfits wouldn't hide her impressive bust. There's also the fact that her sexually provocative design is actually justified in-universe with Mai dressing like that in order to distract her opponents during scuffles. In other words, her sexuality is very central to her character. And finally, Sakurai is a guy who sweats the details, and is adamant about representing these characters as best he can. To wit, the man was unironically going to not include Pac-Man in Smash 4 if Bandai Namco wanted him to use the 'Ghostly Adventures' design. To shrink her bust, cover her up, and downplay her more sexually suggestive mannerisms, would be to completely remove most if not all of her most defining traits. It wouldn't be true to the character in any way.
An honest to God Direct on 7-20-2020 would be kind of funny since the E3 presentation was supposed to be on 6-9-2020. It also kind of drives me nuts because if Hotgirl was telling the truth about a delay then the 7/6 stuff is now probably on 7/14 and 7/14 is now 7/20.... This year, man... This year... Who pissed in God's Cheerios?
I couldn't hold it, I'm sorry.