i think the best thing for nintendo to do for smash ultimate on the switch 2 would be adding more skins to fighters and even stages. they wouldn't be just normal old recolors either, i'm talking unique stuff like what the modding scene has done. funky kong DK, ranger marth, KH cloud, sunshine mario, dry bowser, shadow over sonic, totk/phantom ganondorf, oot/ss link, venom/naked snake, wedding bowser, raven beak on dark samus.... the list goes on. for stages you could get things like melee/brawl FD/battlefield at the very least, but i'm sure they could do some things that are a bit more robust than that too.
honestly, i always wished they would have sold costumes like that in the base game. like, hell yeah i'd pay a dollar to play as kh cloud officially instead of needing to get a hack for it that may or may not have issues.