I wanna clarify what I was saying
My "logical pattern" was that the third party reps would all be protags
Which would make sense in most cases. Protagonists are generally the most recognizable and popular characters of their respective games, hence why it took so long for us to get some villains in Ultimate. Smash 4's DLC were protagonists as well, so overall that's not an unreasonable expectation.
Even though we know said leak had nothing to do with Smash, it still wouldn't surprise me if this came to pass.
Cygames is ****ing huge in Japan now, and they have the connection with Nintendo through Dragalia Lost, and Nintendo owning stock in the company.
It's huge in Japan, but how many people outside of Japan are going to care? International appeal is important when determining characters. Sakurai has considered and then disregarded characters multiple times because he knew that they wouldn't have any appeal outside of Japan (like Takamaru). Chrom was said to be added to appeal to Japanese players, and Dark Samus was said to be added to appeal to Western players.
The only way they could get away with that is due to the Fighter's Pass, since people have already purchased it, so they can throw in whoever and people will still have technically paid for it. But given Sakurai's attitude about "Don't buy it unless you're confident in the characters we'll add," I don't think he'd throw in a character he knew would be unappealing to large chunks of the playerbase.
Even then, part of the reason people considered a Cygames character to be possible is because of that mentioned business association with Nintendo, and the cynical belief most people had that Nintendo would make all the DLC characters corporate promotions. Then we got Joker, who is a character from one of the highest-profile Playstation games of 2017, so I think that line of reasoning no longer holds any merit at all.
Inkling and Joker are good middle-ground characters who appeal to both spheres. Splatoon is
huge in Japan, and so is Persona. But they're also very popular in the West as well, so no side is left shaking their head that the character solely exists due to foreign appeal.