Seriously, the witch costume looks way off for me too. It was using some of Peach's model I think that giving her witch mod her normal gown, except a huge slit in the front that goes near her knees, and then put in her legs. She would probably have thicker arms, like she does in Ultra Tennis and then give her the witch hat. Not only would this be bewitching, but classy and poise (in my opinion).
Thank you, I was wanting to know how her motherly persona feels from certain angles. Not only how she bears similarity to Rosalina, but how she treats other in Overwatch as well.
So I've thought of her Tennis Dress for a moment and a little wardrobe theory popped in my mind.
I believe that her sport dress is made accessable to every kind of sports, so that she wouldn't need to wear shorts. Her sport dress has a slit in the front, which probably makes it easier to do sports like Equestrian and Tennis, plus her floating around wouldn't be too much trouble. The material her dress uses is suitable for each varieties of sports. I think it would make sense if they gave her this outfit for the Olympics game.