In putting Black Shadow in the game, it's possible for him to not be a Ganon clone y'know.
Honestly, in supporting BS in PM, it doesn't make sense for me to not want Ridley in for reasons of "I can't imagine him being different from Charizard." Like Falcon, Black Shadow is a racer. He's got so much potential for a moveset because one hasn't been defined for him yet aside from him being darkness-themed like Ganon. The PMBR could do literally whatever they wanted to with this character, giving him crazy moves and whatnot, because his fighting style hasn't been defined yet.
To make a comparison, Street Fighter is a game that consists of 99% human characters, many with similar builds. Yet Capcom managed to make completely unique movesets and characteristics for similarly-built characters. Look at the grapplers for instance, Gief and T.Hawk have similar moves (circle-throws functioning similarly, like pretty much all circle-throws), are of the same archetype, and play drastically different from each other. Ganondorf ≠ Black Shadow, current Ganondorf is one of the most satisfying characters in the game to play as, F-Zero doesn't have any representation aside from Falcon, one of the hypest characters in Smash.
"Because Ganondorf" is the weakest argument I've ever heard for not wanting a character in the game.
Over-representation is a good reason not to vote for him. I'd drop my votes for Lyn and Goroh in a heartbeat if it meant that exclusively non-represented series would make the 5 slots. Plus, my reasoning behind voting Goroh was "because F-Zero" and my reasoning behind Lyn was "katanas are cool." Might as well just replace both of those votes with Takamaru at this point, his game doesn't have Smash representation and I'd be down with giving him a shot.
I'd even support Pichu coming back if his moveset was drastically different from Pikachu's, but over-representation is the only reason I have why not to support him.