I'd rather they go meta and choose a movie character. Goldeneye was developed by Rare, so maybe James Bond?
I'm not saying I don't support Banjo and Kazooie (I believe Smash Bros. should strive for upwards of 100 characters), but back when the Smash 4 ballot was a thing, I voted for the Incredible Hulk, for goodness' sake. (Or maybe it was Tetris. One or the other.)
Pretty much every blockbuster movie series except Jason Bourne has had a Nintendo game. Vader, Iron Man, and Batman all have the same amount of possibility (almost none but still some), and who wouldn't want them battling Mario?
Okay, back to the topic at hand.
I've never played Banjo-Kazooie, but I haven't played Goldeneye and I still want James Bond. I don't watch DragonBall Z and I still un-ironically want Goku. Banjo-Kazooie seems like a fun series, and I'll play it eventually. The characters seem like a good fit for the crazy, weird, wacky world of Super Smash Bros.. Give me those characters, and Sma5h might be the game to beat Brawl as the best video game of all time.