Let me explain why Snake, Joker, and Bayonetta are allowed in with their Weapons.
Snake uses his improperly half the time, with his Weapons also being stuff an Average Joe on the Streets can’t really buy… at all. Not to mention how Snake actually got his Landmine changed during Brawl’s Development, so CERO stepped in and told Sakurai to change it.
Bayonetta’s Guns look very fantastical and function very differently in game than a typical, realistic gun, what with having four of them, half of them on your feet being pretty obviously impossible, likely giving Bayonetta a Pass by CERO considering her sex appeal was also censored as well.
Joker is a little trickier, but Joker actually does use his gun
very improperly in Smash. Joker’s Gun in P5 is the TT-33 handgun, which is normally used like
this, and is used with one hand, a more traditional way to hold a gun, even if still inaccurate in P5 anyways, but Smash exaggerates it far more, with the posing and
especially Arsene’s Powerup making it clear that this gun is more fantastical in nature than its TT-33 Inspiration. Essentially, Joker did just enough to maintain a CERO A that honestly I’m genuinely shocked that it wasn’t cut entirely lmao.