I'd like to sign up as a Banjo supporter, though my own thoughts on him are fairly complicated.
I'd like to first say that my only experience with Banjo-Kazooie was playing a demo of it at a BestBuy for 15 minutes as a kid, so I have no nostalgia to influence my judgement.
Banjo-Kazooie is a strange one to me. I understand that it was a great duology of games, and even Nuts n' Bolts was a very bold and interesting game that was unfairly shafted by ill-fittingly slapping the Banjo franchise paint on it. However, I never understood why so many people seemed to clamor for it in Smash or believed it to be an iconic series on par with the greats like Mario and Zelda. Again, I totally respect that it's a great Platfomer series, but it was just one of many in the golden age of great Platformers. Just off the top of my head I can list Mario, Donkey Kong, Crash, Spyro, Rayman and Sonic as franchises that dominated the Platforming scene from the mid 90s to the early 2000s and there's probably a lot more that I missed. To me I just didn't get that hyped about seeing two former Nintendo mascots with a vibrant but short history get in over the loads of 1st and 2nd party characters that could be added in instead or interesting 3rd party picks that didn't have a messy breakup with Nintendo.
Looking at it now however in the context of Ultimate, current relations between Nintendo and Microsoft, and some old words from Sakurai himself, I find myself more and more intrigued by the possibility of seeing the bear and the bird in Smash.
I know not everyone believes this but I really think that this might really be Sakurai's last Smash game. Everything about this game seems to be Sakurai doing absolutely everything he wants/wanted to do with the franchise, to lay it all on the table before age and health issues catch up with him, and truly make this game worthy of being called the ultimate Smash experience. One of his considerations for Smash 64 was Banjo, but things didn't work out and after being bought by MS all hope of getting him in was dashed forever. If given the opportunity, it might be possible he'd like to add them in and get the opportunity to play around with them the way he didn't have the chance to 20 years ago.
The second part of this that interests me is the relationship between MS and Nintendo. Though obviously they're competitors in the gaming market, the two do seem to be making overtures towards being friendly rivals, with Minecraft getting ported to the Switch. With the buyout of Rare being so long ago and all the messiness of the transaction being swept away by the passage of time, I honestly think giving Banjo's and Minecraft's licenses to Smash would make an excellent peace offering to Nintendo, and if accepted could open the door for easier behind-the-scenes deals between the two companies.
If MS really does get representation, I think the ideal way to do it would be to have Banjo as a playable character, with possibly a Minecraft stage to come with him. Let Banjo, the MS franchise with the most history with Nintendo, be the link between MS and Nintendo, as a show of how much things have changed in almost two decades.
As a Halo fan I'd also love to see Master Chief as a MS rep for lols but that is way too stupid for so many reasons.
I was such a big Duck Hunt fan, that I still keep the support picture I drew for him in my signature here... Duck Hunt was the last remaining Nintendo icon from the NES era that wasn't playable in Smash Bros., and so that's why I was a huge supporter of him getting in.
I hate to say it, but I would've picked Duck Hunt over Banjo-Kazooie even. To me, well, first party Nintendo icons ought to have priority. But, eh, Banjo-Kazooie is a pretty big Nintendo icon despite being 3rd party and used to be 2nd party... Still, that Duck Hunt dog is infamous...
Same bro. Duck Hunt is one of my favorite additions to Smash and is incredibly fun to play as in Smash 4.