I quoted because I want a Excuse to talk about Shadow again, because there is something I got to add
Someone already linked this video on this thread, but Blastbox had a viewpoint on Fighter Pass 2 so far
His viewpoint is similar to the viewpoint of the 2nd chance theory that was (and is) popular in speculation. However one interesting observation occurred to me through this video
Fighter Pass 2 isn't just adding more fighters to the game, but it's also fixing holes in some of the representation in the game, in terms of what Nintendo and Sakurai intially envisioned for the game
-Steve and Kazuya are representatives of Franchises that Nintendo had wanted to be represented in Smash, but due to complications couldn't get in intially.
-Sephiroth helps makes the FF7 game feel much more complete in representation. However don't get it twisted, Sephiroth was the main reason for the Filling, He was just the vehicle for the other extra stuff (Music, Spirits, etc) to come with
-Min Min and Pyra/Mythra both showcase the Switch Library that people enjoy, which is usually something that has to wait a whole other Game and Console generation, but thanks to DLC can be included on the roster
Looking from this angle, while there are certain franchises (Kirby, Zelda, etc) that could fit this, Sonic is probably in an egregious situation since there are 2 main complaints that need to be addressed
-Despite the Large Popularity and Iconic status of the series, and the fact that the Sonic Supporting cast is among the most Iconic and popular in terms of gaming, along with Sonic being present in More Smash games than there ever has been, Sonic still only has 1 character to it's name
-While Sonic's Moveset is technically accurate, it has a lack of flair for alot of people, that people wanted to See when they envision Sonic in Smash
With that in Mind, Shadow specifically would be able to make the Sonic Representation more filling, though these reasons
-Addressing even getting a Sonic character, that's something more general any Sonic character can do, Like Eggman, Tails, & Knuckles. Shadow is the 2nd most popular character, the character the Head of Sonic Team (and maybe Sakurai) likes the most, and is the Sonic game the Japanese really love, along with SA2 being one of the few really high selling Sonic games there (along with SA1, 06, Unleashed, and OG Tilogy), so he can fill this role greatly
-Something Shadow does specifically is "Add a Sonic with more Flair"
As much as I am against the Idea of Sonic being an echo, in terms of his Creation and overall attributes, Shadow is an Echo of Sonic, a Reflection of the character. Both are very Speedy Hedgehogs, that Live free and make their own destiny, using the powers of not only themselves, but their friends. Shadow is just the Darker, more on Edge Interpretation of that. as an example, Shadow was the way that Sega was allowed to make a Game where "Sonic can use Guns"
In terms of Smash, Sonic is most likely not gonna get substantially changed because of Sakurai's Unwilling to make Drastic changes to Characters (even then, I Imagine it's harder to do with a 3rd party character like Sonic), and that I think they want to Keep Sonic simple in Concept, and more derived from his Classic Appearance
However Shadow is the way to add a Sonic that has more Flair and Complexity to him, without having to get rid of the old Sonic moveset for those that like it. Shadow is still just as Cocky and Confident as the Blue Blur, but he has a more added brutality, Focused, and Edgy nature to the way he portrays himself.
They can add more of the Modern elements onto Shadow in terms of Animations and moveset since Shadow is solely associated with the more Modern era of Sonic, This can include stuff like the Boost Attack, Light Speed Dash, Black Tornado, etc
Like how Kazuya has the Devil Gene to add more Flashiness and Complete moveset to the General Mishima Tekken Moveset, Shadow has his Chaos Powers to Make the Moveset Complete and Flashy, along with adding some Complexity. While Sonic is more general in terms of the moves he does, and focusing heavily on the General Core of his arsenals, Shadow would trade a focus on some of the General Abilities of Sonic (Spindash, Homing Attack) for the Added Versality of his Chaos Moves.
Of course the Chaos Moves would be his Specials, as Chaos Control, Chaos Spear, Chaos Warp, and Chaos Blast, with Super Shadow being his Final Smash
In terms of Gameplan, for those who wanted a Sonic that's more focused on the Aggression instead of the Hit and Run of Sonic in Smash, Shadow is a perfect character to represent that
These are the things Shadow can do to make the Smash Videogame more Complete. Sonic is also a Huge franchise that is still relevant to this day, getting Games, Movies, Cartoons, and Crossovers either right now or coming in the future. Sonic and his Cast of characters are not leaving, and I think that's a good reason for Nintendo to be down with adding in another Sonic character, and Sega themselves want the Sonic I.P to be the greatest it can be, first and foremost. It was Sonic that got into Minecraft as an example