*CRAZY THEORY MODE ACTIVATE, HUGE POST INCOMING*
Let me introduce you to something I call...
The WAH theory...
Hear me out, i'm gonna say this before Fighter 5 gets leaked and i'm totally wrong...
Fighter 5 might actually be ****ing WALUIGI.
https://twitter.com/NanaKarobi/status/1200208052479315968
*People have told me that this account is a sabi alt or related to him in someway but I can't find anything to confirm that*
*EDIT: Sabi has confirmed this is NOT his alt*
This is the Paragon leak. It came right before E3 and was one of the few leaks to guess LUMINARY over Erdrick. Luminary is key here because we know for a fact that the Dragon Quest character was never going to be just Erdrick alone. Now, it's possible that Erdrick may have been planned to be the default costume at one point, but the fact that Luminary existed from the get-go, the fact that he represents DQ XI over just DQ in general, and the fact that he would be arguably more relevant overseas compared to Erdrick, contributing to a more worldwide appeal, even if mainly aimed towards Japan makes me think he was probably always destined to be the default.
Now obviously the big fly in the soup here is Frisk instead of Terry, but I have talked with Paragon about this and I distinctly remember him saying (even during late E3 season when this leak was a hot topic) that Frisk is more of a general prediction towards Undertale content. And basically, Paragon assumed a fighter due to the music existing because no Mii Fighters had ever come with songs before. AND, his prediction of not Sans did end up true, to be fair. The whole thing is summarized really well here, with Paragon correcting some of my misinterpretations.
Now, Paragon says he agrees with Fatmanonice here in that Waluigi is not Fighter 5. (Fatman himself doesn't comment on Waluigi understandably, because of the prospect of death threats similar to the ones Paragon received, but he has said on Discord before that he believes FP 5 likely isn't a first party character, which is a category that Waluigi undoubtedly falls under)
This is where Imran Khan comes in. If you guys don't know he's basically a resetera dude from GameInformer and has an extremely credible track record. He was one of those "big guys" who went seriously against the Grinch leak. Think of it like this, in terms of where he stands in credibility, call him Shinobi's Echo Fighter.
If you watch Imran's reaction to the Sept. 4th Direct from a backup of his livestream that day, he clearly knows about the extra fighters, and then goes onto claim that Nintendo made the decision to do extra Smash Bros. Ultimate DLC around E3 time. What's worth nothing is Paragon heard Waluigi AS EARLY AS FEBRUARY, and he heard that he was "last".
At one point, the Final Fighter's Pass character was going to be the last new Smash character for a LONG time, and most people assume that the next game will be a reboot, making the prospect of new characters slim. Waluigi is obviously not in line with ending on a character like Incineroar or Bayonetta, but that's not to say he wouldn't be a controversial ending to many people, that's pretty hard to deny. In that sense, I think he makes perfect sense as the "ultimate ending, the ultimate troll, the ultimate whateveryouwannasay". I can see at one point that this would be the character that Sakurai would decide to basically end Smash Ultimate on.
And then to end this off, i'd like to conclude on going back to Jon's video posted today, where he went ALL in on Spirits and Assist Trophies not deconfirming anyone for DLC and specifically made points about fighter 5 potentially being someone like Rex and Pyra. Obviously Jon wouldn't flat out say who the character is in a GameXplain video, so this makes me think this is a cover up for a different character. Notice how Jon specifically didn't mention obvious candidates for upgrades like cough Geno or COUGHCOUGH Waluigi. I specifically don't think Rex is DLC 5 (even if he still could be post pass) because of this statement:
Keep in mind, Jon made a similar stance on the Grinch leak, even went as far to bet he would have to sit in a wet puddle for a long time if the Grinch was real. He sounds really confident in this and I doubt he'd go all in on this like he is if he was to be proven wrong and the rest of DLC would just be third party characters with no Assist Trophies/Spirits upgraded.
And with that, I think my stance here is concluded.
I COMPLETELY realize that this may end up looking incredibly stupid when Lloyd or some other 3rd party we could have expected ends up being DLC 5, but I think it's still fun to speculate around the information we have now.
Feel free to look at this and laugh, say haha stupid theory this guy knows jack **** about what he's talking about. But like I said, it was still fun to form such a speculative theory that goes a long distance from what type of characters most people predict from FP 5. If you dislike Waluigi, please try not to attack me i'm not saying you have to like him or anything, i'm just forming a theory around him.
TLDR | Waluigi is Fighter 5, Geno very good shot for post pass
Consider this V1.1 of this post since there might be some edits I need to make later.