I want a robust single player game. Classic Mode going back to being... well... classic, is a big step in the right direction, and i'm loving that each character has a classic mode that's tailored to them with their own title, but of course I want more. I expect target smash being tailored to each character to return because of this.
I want an adventure mode, of course, likely something between Adventure mode in Melee and SSE from Brawl. What I'm expecting is something about the size of SSE, but with little to no cut-scenes, the trade off being that the locales and enemies and bosses all come from represented games instead of being generic locales with the Subspace army and the occasional Koopa Troop member... of course it's possible we'll get nothing, and i'll be sad, but not devestated.
I'd like My Music to have an option where you can make a playlist for each stage that has whatever songs you want on it instead of restricting you to series... I want this so I can play Gangplank Galleon on the Pirate Ship level. That is my only reason. Also I have to wonder where songs from the "OTHER" category will go if everything is organized by series now.
If trophies are returning, something from Melee that I'd like to come back is classic mode trophies using classic designs for the characters. In melee, a fighter trophy you got from adventure mode used their model from Melee, but in classic mode it was more closely based off of official artwork from specific games, even re-creating specific poses. Mario and Peach looked a lot like their designs from the 2D Artwork, Bowser had colors and proportions similar to his SM64 renders, Yoshi was based on Yoshi story despite his model in melee being based on Yoshi's Island, ect.
I think it'd be kinda cool if you could arrange the CSS any way you want. Seems like this time it's based on their numbers, but i'd rather group them by series. I also don't really want Echoes next to the characters they're based on.
Lastly, more costumes. I've wanted Sakurai to go all in on costumes and skins for so long. Some of these characters have so many different designs through out their series, or they have their own alternate costumes, it seems like a wasted opportunity to be so stingy with who gets to have a true alternate costume and who doesn't. I wouldn't even care if they were DLC packs.
EDIT: OH yes, one more thing. I want fighters that nobody is playing as to have a chance to pop out of an assist trophy and help fight for a little bit. Think of it like Ditto, except instead of turning into whoever threw the ball, it can turn into anyone who isn't on the stage.