My school actually had a different summer and winter uniform. I think that's a bit much but I have said before, the PE kit should be suitable to be worn when we do have temperatures hitting the 30s.
I also think there should be more choice, flight attendants all used to wear something similar to a school uniform but more recently they have introduced more options (OK not all airlines) I think BA has options of a jumpsuit, trousers, dress or skirt and a tunic / trousers combo.
I've taught girls who will not remove a jumper because their shirts are thin and show their underwear.
My cousins in Australia had a sort of uniform at primary, it was basically red, white and blue so you could wear trousers, skirts, shorts, pinafores.
On PE day they had to have something suitable for PE but it could be something you took in or you could spend the day in a tracksuit.
It seemed to work well and allowed for different sizes and shapes.