I personally would much prefer the last 2 newcomers to be first party. But the way it’s been going, it looks unlikely. Anyways, here are some first party newcomers I’d like to see/think are likely, be it as DLC for this game or newcomers for the next game.
1. Porky. Probably just the EarthBound fan in me, but this would be my above all dream pick. There’s some “evidence” it could happen seeing as he doesn’t have a Spirit yet (he’s the only Smash Bros. Boss without one), but I know it’s still unlikely. Regardless, someone made up this awesome moveset, and I think it would be really great in Smash. He’s the last true villain from the series that are represented in Smash 64 (minus F-Zero, which I don’t know much about so I don’t know who the villains are besides Black Shadow) and I’d love to see it happen.
https://m.imgur.com/a/yRRMP6t
The rest are in no particular order (just the order I remembered them in my head).
2. Dixie Kong. With K. Rool in, the last prominent DK rep is Dixie. Could borrow some things from Diddy, but would have a mostly unique moveset that implements her hair as an up special and possibly a few other attacks.
3. Rex and Pyra/Mythra. Sakurai is already a fan of the Xenoblade series, and I personally don’t think Mii costumes deconfirm characters. Don’t know much about Xenoblade but I’m sure Sakurai could create something unique so the character doesn’t have a similar moveset to Shulk. Only downside to this is that it’s another sword character.
4. Bandana Dee. The not-as-important, important, 4th Kirby party member. We have the core 3, but if we get another, Bandana Dee I think would be next in line. A unique spear user who could bring an interesting moveset to the game.
5. A Pokemon Sword and Shield Rep OR FE: Three Houses Rep. Basically would be put in to get hype for the next game in the series/further the hype for the game. No idea how they would work yet. Downside is we get another character from a series that already has a pretty good amount of representation.
6. An ARMS character. Spring Man is already an AT, so that eliminates him I’d think (same reason Waluigi isn’t on this list, though I suppose both could get an upgrade in a future game). But that’s OK, I feel Spring Man would be a bit generic. But it still leaves the door open for others. Helix, Mechanica, Kid Cobra, Byte & Barq, or any of the others (including the ones that already have Spirits, but I’d give them a lower chance). I guess they would kinda function like a longer ranged Little Mac? But I’m sure Sakurai could incorporate a few new ideas to keep the character fresh.
7. Krystal. AT upgrade, could bring an interesting moveset. Not a big Star Fox guy, but I assume her staff freezes people in those games too? Feel free to correct me if I’m wrong. That mechanic plus using the staff as is for attacks could make for a unique moveset.
8. Sylux. Again, don’t know much about him, but he’s apparently missing from the game entirely as of now, which I do find odd, whether he’s the main antagonist in MP4 or not.
Last mention goes to a character I’d like to see as an Echo Fighter, and that would be...
9. Octoling. I mean, it’s a pretty easy Echo I’d think to put over Inkling. And from what I saw, there were a lot of people who enjoyed the Octolings once they were playable in Splatoon 2. Don’t know that it’ll happen since they’re avoiding Echo Fighters for this pass, but maybe after the pass along with 1-2 other Echoes? I dunno.
Again, really hope the last 2 are first party, however unlikely it may be. But even if they’re not, these would be my candidates for a first party Fighters Pass or first party newcomers for the next game.