My main hope for a DLC character, which isn't going to happen, is Shantae. Even if she eventually gets added, which unfortunately is very unlikely, it wouldn't be tonight on such a large stage.
Seeing a lot of mention of some character from Fortnite. I'm not a shooter game player and I have no interest in this game whatsoever, but I realize that it's popular and is a suitably big name title that Nintendo might want to use to boost sales. As with any character, I'm fine with them as long as they're fun to play, so if this rumor ends up being true then I hope the character has a good moveset. Even so, I wouldn't really be excited about it or anything due to lack of personal attachment to the game.
Another suitably big name that could potentially happen, that I'd like to see and that would probably fit the award show, would be the Doom Slayer. Admittedly, I've been swayed by the memes of Isabelle and the Doom Slayer, but I think they would be a pretty neat addition. It would also be pretty great to have
At Doom's Gate added to the soundtrack.
Another addition I'd like to see added that probably isn't going to happen, but has probably a better likelihood than Shantae, would be a Mortal Kombat character, most likely Scorpion. There'd be no blood or Fatalities or anything of the sort, but I feel like since we have Street Fighter and SNK represented, they ought to add more fighting game series into the mix. This would also mean that it would be nice to get a Tekken representative, which honestly is far more likely than Mortal Kombat, but I mentioned Mortal Kombat since I'm a bit more attached to that series. Either or really, though hopefully both series get a representative added someday.
Whoever it is, I'm looking forward to finding out who the new fighter will be.