Kazuya definitely seems to fit the bill of "truly extra" like the other fighters in pass 2. Other than perhaps Sephiroth, who still has mechanics to make him stand out but is kinda same-y to other characters, these pass 2 fighters all have whacky gimmicks and movesets that really set them apart and it's clear that Kazuya will dip into some more of those crazy fighting game mechanics in a way other characters haven't quite tapped into to the same degree. The problem we have now is that that there are so many characters who can bring something new to Smash and have whacky gimmicks and very involved movesets and like
TooManyToastahs
said tie up loose ends that we still really don't have anything to go off of in terms of speculation. Rayman ties up loose ends and can bring a zany moveset as could Geno or Isaac, etc.
After all this time it has become kind of apparent that Nintendo really probably did just say "wouldn't it be cool if x was in Smash? Can you do that Sakurai?" And Sakurai was just like..."I'll do that but to the most ridiculous degree possible." The only rhyme or reason here is just what Nintendo thought x character would be cool and profitable and Sakurai just ran with that. I think that's the message here and that is both good and bad for speculation. It means there's really not much of a pattern to follow, but also Nintendo clearly has a broad idea of what's cool and profitable so that means we can kind of just justify whoever we want. The only real rule seems to be no non video game characters. It's funny because that's what many of us have been saying since the beginning but people, including myself, were determined to create rules.
I'm not sure who will be last. I am wondering if we will end on a high note or not. Maybe it'll be first party. Maybe Master Chief really will finish the fight. Maybe Geno will grant our wish in spite of my many doubts about it. At any rate, Kazuya has given me a strange peace about the whole thing. I feel like I can finally just enjoy this again. I'm ready to see who this last character is and be excited for their fanbase. I think it's exciting that Smash has made such a name for itself that we have SNK vs Capcom vs Tekken vs Nintendo. The matchups in Ultimate are so insane. I never would have imagined a roster like this and I'm grateful for it. I believe the Smash series will continue and that Ultimate proves that, despite any roster cuts, Smash will always make a name for itself and go above and beyond to give fans an experience they can't get anywhere else. It's truly wild.