Okay so it's been a couple days and I have a better understanding of Banjo. Enough to know that I'm DEFINITELY maining him. I still doubt he'll end up top tier, mainly because his recovery is a bit too punishable, but I think he'll end up high tier, probably a little above Ike.
His down B is going to be one of his strongest tools, I think. He can drift so far while launching it and he's active so soon afterwards that he can use it to force the opponent to make a reaction, and approach by beating the opponent's reaction to the bomb. He can also use it in tandem with the egg to play the zoning game, but I don't think that's going to be his forte. Still, it's nice to know he can create and maintain distance when he needs to, should be useful for things like waiting out Arsene.
His dragdown combos seem a little inconsistent. I believe it was Coney who mentioned on Twitter that whether or not he can consistently find strong drag down combos will likely determine how strong of a character he is, and I agree. He's fast enough and hits hard enough, but he doesn't have a lot of confirms. His fair is safe enough that you can use it against campier characters to break a wall, since it isn't heavily punishable but it hits hard enough that they're forced to respond to it, so characters like Olimar and Belmonts have to stop throwing projectiles if you can find a way in with fair.
The recovery mixups are almost good enough to make up for how incredibly unsafe he is off stage. Drifting while dropping a bomb is already a better horizontal recovery tool than any of the Marth clones have in their kit, and the fact that you can drift into your own bomb and grab it for a bomb recovery is rather useful as well. Side B as a recovery tool is a solid Hell Mary, but it has enough wind-up that I've been killed before the armor kicks in more than once now.
Spring edgeguards are surprisingly disappointing with Banjo. The spring is so big that you have to go way too far off stage, and it takes too long to get that far so your opponent can already be back on stage before you get out to the spot you want to drop your spring. He doesn't need it, though. Bombs make edge guarding and ledge trapping a piece of cake.
His side B having 5 charges only gets really scary because it's such an important recovery tool. If it was only useful on stage, 5 would be more than enough and you would never notice. AFAIK there are still no confirms into his side B, so you have use it as a callout. It's still a pretty useful tool, even though it's a huge risk every time you use it. It can also be used to punish techs. If you time/space it properly, it will cover tech in place and tech away, and get you far enough away that it's difficult (in some cases impossible) to punish if the opponent decides to tech in.
Fsmash is just straight up Lucina's fsmash with a different sound effect. Catch a landing with it or use it to whiff punish, and it starts killing near the edge at like 70%. And with your damage output, that's just like two little two piece combos that'll get you there.
I could keep going. There's a lot of cool stuff that this character has. He also just feels so natural to the game. Like, he doesn't even feel new, he's so intuitive and comfortable. Part of that is that his entire kit is almost entirely made of tools that already exist on other characters, but that's not a bad thing.
EDIT: Hoping for more first parties from the extra DLC. At this point, I'm so satisfied with Banjo that I can't really think of any other character I would even be interested in playing that also have a chance to make it in, with the exception of Dixie Kong. Ray from Custom Robo might have a shot, which is a character I would love to be able to play, but he would also almost definitely be a zoner and I don't wanna do that. I would love for Sora to make it into Smash, he's probably the only third party character I'm really interested in at this point, but even then I don't think I would actually play him because Banjo is so god damn fun.
Anyways TLDR I really like Banjo.