I may as well go with a console I still think of as pretty cool, that being the Nintendo DS!
1. Reporter and Wrestler, who I think would be an out-of-left-field pick for a Rhythm Heaven rep whilst still a popular and well-known one. I'd like to imagine you'd play as the reporter, but could occasionally bring in the Wrestler as a sort of semi-puppet archetype - though Reporter could still have plenty of references to different Rhythm Heaven characters and minigames in her moveset.
2. Serperior. I felt a Pokemon rep would be a really important inclusion, and given we already have Lucario as a Gen IV rep, a Gen V rep makes a lot of sense too. Whilst I have a few of my own favourites here - ideally Golurk, Genesect, Chandelure or Accelgor - keeping with the tendency to go with starters feels like a safe bet. Serperior's also in a cool place where they can represent the Grass typing, and has a pretty unique body type that'd help them feel pretty different.
3. Maxwell, a unique third-party pick who I think - whilst from a slightly less popular series than some of the others here - would be an awesome inclusion overall. Scribblenauts is an interesting series to delve into that a lot of people would say peaked during it's earlier years - but Maxwell does still have plenty of potential for a unique moveset and vibe unlike any other. Also, his costumes could represent different characters from the series!
4. Cooking Mama, who again represents a pretty unique genre, would also be an awesome inclusion overall. Her moveset would mostly centre around cooking and the use of cooking utensils as well as foods - plus, it'd allow her to fight with some really weird and wonderful things. Cooking Mama was one of quite a lot of "real world" simulation games for the system, and whilst there's plenty of options, I feel like My Stop Smoking Coach doesn't lend well to smash.
5. Dr. Kawashima, given how incredibly popular Brain Age both was and is! Given his nature as a puzzle rep (and a giant head), I'm sure his moveset would be very unique and interesting - and his inclusion would be a weird, but pretty cool addition overall.
6. Professor Layton, a third-party pick given the series is owned by Level-5, but one tht works pretty well as a DS representative overall. With the first four games in the series being released on the console - and some of their games being the best-selling on the console as a whole - it makes sense to include them. Layton's own moveset, also, could be an awesome one - with a mystery-centred theming - plus a couple of appearances by his assistant, Luke!
There were a few characters I considered for this lineup - picks like Neku from The World Ends With You, Vince from Art Academy, Sissel from Ghost Trick, and some others came close, but I struggled to justify them for their own reasons - usually that they didn't maintain as much popularity in the modern climate, or that other characters would do a great job at representing their own series (and genres!) in cool ways. Serperior could probably also be changed out - but I think a Pokemon character would be a logical pick overall. Even so - I think this is pretty solid. Ish.