King K. Rool: (Very Likely) He's the new generation's Ridley. The well beloved big antagonistic Rival to the main character. He's big, mean, and would definitely be a nice thing to see in Smash
Ashley: (Rare) While Ashley has a lot of following, the character doesn't really hold enough Star Power for her to be included in Smash. The inclusion of her own assist trophy is notable in her list of achievements, but so did Takamura and Waluigi...
Geno: (Plausible) Geno has been widely asked for ever after Brawl came out, I'd honestly be super ecstatic if he did make it in here because he's the posterboy for wanted Smash Characters. With his costume in Smash 4, it seems like Nintendo knows all about this. I'm hoping that he'd at least be DLC.
Black Shadow: (Rare [For new Character]) (Likely [ For Echo]) Not a popular character overall, but he is the biggest pick out of all of the F-Zero characters for his "Ridley" factor. While not being a huge threat to Falcon (even being humiliated by my boi Deathborn in GX), he is an iconic rival to the racer... which could make him a good echo.
Simon Belmont: (Very Likely) His reasoning kinda follows the DLC fighter's reasonings... He's the MC of a popular Konami franchise. He's also the most well known outside of Alucard or the recently popular Trevor. There's also well backed leakers who are saying that he may be included, so there's a chance that may be true.
Elma: (Plausible) While not a MC of Xenoblade X, she is a popular character from that game. Though a 3rd Party side character has never entered Smash Before, I think that Elma wouldn't be a bad start.
DOOM Slayer: (Rare) DOOM Slayer is too western for the tastes of Smash, he is too American for this game. However, he's the most popular western video game character there is. He's got a lot of credinetlas and charm to him... And let's be real here... you really want to see Mario get a chainsaw to the face..
Isabell: (Plausible) Out of everyone here... she seems to have the least amount of moveset potential... I mean, they could flub it, but it's not fitting to her character. I do think she would be better off as an assist trophy, but leaks have said she would be in... so there's a gathering towards her.
Eggman: (Plausible) While he is very low on lists... I think if there was ever a 3rd Party non MC in Smash... It would be him. His mechs could provide an interesting new creation for Smash Bros, using moves from classic and modern boss battles.
Marx: (Plausible) Marx would be cool and honestly I have a soft sport for him... But he's kind of overshadowed by the appeal for Bandana Dee instead... Which is kind of like asking for Blue Toad from NSMBWii.
Bandana Dee
Somewhat Plausible) While the most revered, he's kind of the Blue Toad of the kirby games. He's not meant to be memorable, but rather a generic 4th player. Star Power is kind of a thing when it comes to Smash
Rayman
Very Plausible) Ubisoft and Nintendo are getting tighter... and Ubisoft did also create a Rayman model for Smash 4... so I bet that there's some chance of him being in... but then again... no leaks are talking about him...