I'm legit surprised no one has mentioned the Dragonborn yet. You would think people would take more notice on one of the games that were shown on the reveal trailer of the Nintendo Switch.
Yeah I feel this could easily be a sleeper pick. afterall one of the main reasons Doom Slayer got alot off support speculation wise, was that Nintendo and Bethesda did have discussions regarding Smash.
It would also fit in with how the first Fighters Pass was designed in the first place and that is that the character pool came from the early switch days.
Hero is basically a stealth promotion for DQ11, which was the first Switch title to be announced to be in development when the Switch was still Code named NX
The SNK games where released very early on the Switch's life on the Eshop and sold really well, which leads to Terry Bogard
Banjo offcourse made it because of major fandemand (Ridley and K.rool tier of demand), but Microsoft did support the Switch with some of their previous exclusive indy titles like Ori and Cuphead
Joker is the only weird case I guess, but I guess he could have been chosen because at this point he is Atlus's Cloud and Shin Megami Tensei has huge Nintendo history. (Fandemand perhaps is a reason to, because Persona 5 has become huge)
Skyrim was one the first games to be announced to be ported to Switch to show off the strenght of the console, so it fits perfectly well with how Nintendo potentially decided the DLC list and unlike Doom, I believe the Japanese atleast like or are familiar with the Elder Scrolls games.
As far as I known the Cacodemon Mii costumes have yet to be deconfirmed to, so maybe that costume is part of a Bethesda pack?