Anyone who seriously tries to argue it can't work is deluding themselves.
She can't be Lazy Daisy for sure (nor should anyone), but saying she can't be an Echo period is asinine when we have the likes of Ken and Chrom having notable different attacks from their source.
There is nothing Diddy can do that Dixie cannot imitate as they have the same exact frame with the only difference being the lack of tail....which doesn't matter because Diddy doesn't use it in Smash anymore.
Take Diddy's moveset and then:
-make the running speed slightly lower (just like how
is slightly faster)
-make her Helicopter Spin for a Dash Attack just like DK's roll and Diddy's cartwheel (just like how
again has a number of different neutral attacks with kicks)
-replace the Up B with a move similar to DK's since Spinning Kong was based on Dixie's hovering technique in the first place (just like how
has a move like Ike's Aether instead of Roy's Blazer)
-give her DK's Cargo Throw for heavy items using her ponytail.
-swap out peanuts for gumballs for Neutral Special (aesthetic change, but she was straight up given a Gumball Popgun to mimic Diddy in Tropical Freeze)
There. You have Dixie easily with nothing that looks out of place as an Echo that like Ken, pushes what defines an Echo.
EDIT: Oh, and a different Final Smash got obvious reasons.