I had Crash in my roster instead of Steve for awhile, but I'm not super confident on him. If we got four third parties, I would be extremely likely to include him. That said, I could see him getting in and not Bomberman.
Could I ask why you see Rayman as unlikely? I can understand Steve and Sora, but what about Rayman?
Sylux is an admittedly off-the-wall pick from me. I just think he's more likely than Ridley, but still think Sakurai will want to include another Metroid character. Dark Samus is one I've considered as well.
My roster is actually sorted almost entirely by series debut, and Takamaru's game was made with the Zelda engine in the same year as Zelda, Metroid, and Kid Icarus.
It's not a personal want roster, actually. This is my prediction roster, ie, what I see as the most likely outcome. I'm asking for critiques based on likelihood, not want.
Waluigi is actually a character I considered strongly. He's heavily requested and could easily be the representative of the Mario spinoff titles...however, I don't think he'll make it before Captain Toad, and I'm a little wary of predicting a second Mario character while also predicting two DK characters.
I considered Dark Samus as a clone, actually. The clones I can see happening are Funky, Dixie (though I expect at least a semi-clone from her), Dark Samus, Impa, Isabelle, Tom Nook, Alph, Octolings, and Ribbon Girl.
I compare it to Dr. Mario. He didn't steal a spot from any Mario characters, but was simply a bonus inclusion after the game was finished.
That said, I could see K. Rool in place of Dixie or even alongside her. I just don't think either of those is the most likely outcome.
If we get a Zelda newcomer, then who? Impa? I'd consider it, but I don't really see a strong contender in the series, and I want to add a character on their own merits, on not because of fulfilling representation quotas.
Sheriff is a historical character like Mr. Game and Watch, R.O.B., and Duck Hunt; Takamaru is a retro like Ice Climbers, (Brawl) Pit, and Little Mac (Sakurai treats him as a arcade/famicom character in interviews). I have no reason to believe Sakurai will suddenly stop adding historical characters this time around. Regarding Sheriff's potential, did you read what I put in my reasoning? If so, do you not think a coherent moveset can be made out of what I mentioned? If so, why?
In Smash 4, we got Mega Man, Pac-Man, Ryu, Cloud, and Bayonetta. Even if three were DLC, Smash has been consistently including more and more third parties. How is three third parties unreasonable? (This isn't a sarcastic question, I just genuinely don't understand the reasoning.)