I mean
Daisy could have just been there because she was the first new Echo =v
Yeah this is the most likely explanation. Even in the very small chance its hinting towards something else, there's so many different ways to interpret it that it tells us nothing.
Speaking of Arle, that brings up an idea. If you had to choose characters from unrepresented genres (not genre spanners but characters primarily known for a singular genre) who would you pick?
Puzzlers: Lip (Panel de Pon)
Mystery: Prof. Layton or Phoenix Wright
Rhythm: The Chorus Kids (Rhythm Heaven)
Bullet-hell: Reimu (Touhou Project)
FPS: Doom Slayer (DOOM)
FarmSim: Jack (Harvest Moon)
Cards: Hanafuda (Koi Koi)
Text: Kyle Hyde (Hotel Dusk)
There are some genres I'm not as familiar with, like MMOs, and football managers and dating sims, so if anyone can think of previously unrepresented genres I've left out, chime in.
With so many third party characters (and spirits), Smash is sort of becoming a "Museum of Games" so I really like the idea of including reps from more genres. There are is a lot of grey area though, since most genres are poorly defined or contain many subgenres. We'd have a list of another 100 characters if we tried to include every single subgenre, so these are just the ones the ones that stand out the most that should be repped. Your list is a good start though!
Rhythm/Music: Parappa (Parappa the Rapper)
Bullet-Hell: Reimu (Touhou) - Bonus indie character
FPS: Doomguy (Doom)
Sports: Tony Hawk (Tony Hawks Pro Skater) - Cheating a bit here
Sandbox: Steve (Minecraft)
MMO: Someone from World of Warcraft I suppose, but I don't know any of the characters
RTS: Sarah Kerrigan (Starcraft)
Horror: Leon Kennedy/Claire Redfield - Echoes (Resident Evil)
Adventure: Guybrush Threepwood (Monkey Island)
Visual Novel: Phoenix Wright (Ace Attorney)
Edutainment: Carmen Sandiego (Where in the World is Carmen Sandiego)
-Mystery is too small of a sub-genre so its been mixed back into Visual Novel along with Text. Sorry, Layton and Kyle. Technically Visual Novels are also a subgenre of Adventure but I think they're different enough to have a rep.
-Likewise, FarmSim is a bit specific so I would go with a rep for just Simulation games, but we already have Animal Crossing filling that niche.
-Sadly had to cut Puzzlers since we already have Dr Mario, would have gone with somehow having Tetronimoes as the fighter though.
-Dating Sims are also part of Visual Novels, and besides we already have plenty of representation with Fire Emblem and: