I would LOVE LOVE if Daisy was a Pech alt, butI highly doubt Daisy will become an alt because she would have to have flower effects in her attacks, and show pics of Daisy in her Final Smash instead of Peach and also orange boarders. Alternate costumes do not have special effect changes or Final Smash changes. If you look at all of the alt characters in the game, no one has a special effect changes. Not the Koopalings, not Alph, none.
She would either have to be separate in the form of a a clone, a semi-clone, or have an entirely unique move set.
If she did become an alt, here is my idea.
ALL PEACH COSTUMES
First 8 costumes: Peach (dress)
Next 8: Peach (sports outfit)
Next 8: Daisy (dress)
Next 8: Daisy (sports outfit)
So in total, she would have 32 costumes, with the other 8 sets being DLC of Peach in her sports outfit, Daisy in her dress, and Daisy in her sports outfit.
I know 32 costumes sounds like a lot but I feel like a lot of characters will get a lot of alternate costumes by then. Haha I can dream.
OR, if that's too excessive, then just:
Default 8 costumes: Peach (dress)
8 DLC alt costumes: Daisy (sports outfit or golf dress)
So in total, Peach would get 8 and Daisy would get 8, giving Peach a total of 16.