Even though I very much doubt Daisy will be added to the cast, it would definitely be awesome to have her on board, and I'd definitely try her out since I already love playing as Peach.
On that note, I'd prefer Daisy to be a semi-clone of Peach. Her tilts and smash attacks should definitely remain the same (especially her forward smash) but with different hitboxes.
Specials are more difficult to decide on. I think her Up B could still be Umbrella, but maybe rather than it being a multi-hit move it just hits once, and if you hit the sweetspot it becomes a shroyuken much like Luigi's Up B? 'Daisy Bomber' would still work fine as a Side B. Down B is probably the most difficult one since Daisy was not in SMB2 and therefore Vegetables don't really make sense (but then we also have to call into question the float ability as well). Maybe her Down B could be one of the Mario Party circle platforms which, much like Peach's Vegetables, is RNG in terms of what comes out (so for example, a blue platform removes 10% damage, a red platform adds 10% damage, a Bob-Omb 'Battle' platform gives her a Bob-Omb etc.). Also, this makes no sense whatsoever and contradicts what I just said above, but maybe as a Neutral B, Daisy uses Toadette instead of Toad? It makes no sense in relation to the games but would be a cool gag. If not then maybe something Mario Strikers related.
Without Peach's float, though, Daisy's air game is nerfed and so buffs are needed elsewhere to balance her out (assuming she has a similar frame rate and is just as floaty).
I would also say is that if Daisy is added, we kind of need Waluigi in as well. He's as relevant as Daisy within the Mario universe and bizarrely, they always seem to be added as a pair in the Mario spin-off series'. It would be weird to have Mario, Luigi, Peach, Bowser, Rosalina (and Luma), Wario, Bowser Jr., Donkey Kong, Diddy Kong and then Daisy without also having Waluigi. It would just feel incomplete. Not to say that I don't want Waluigi in there as well, he is a welcome addition also!
Not going to get my hopes up and neither should anyone else, but I'm all for it, most definitely.
EDIT: This thread is 32 PAGES LONG?! Even the King K. Rool thread can't hold a candle to that. I could have sworn he was the most popular character request? What makes Daisy so popular all of a sudden?
I guess we'll never know