I have been in health clubs in Germany and Switzerland where the changing rooms have been mixed and open. The first time I went in one I thought I had walked in the wrong one but to be honest it felt quite natural and it also meant families could stay together.

Hello. Regarding the possibility of mixed sex/gender gym changing rooms and showers, I find find your last sentence interesting; If that happened I might find myself spending more time in the changing room and shower than in the gym itself!

May I ask WHY you feel that you would need to spend more time in a unisex changing room, unisex shower or at the health club itself? Thank you.

Interesting to find out that men also feel uncomfortable when the script is flipped.

There's a principle I can agree with

If it is a "bar" that serves food, it's no longer a saloon.

Maybe there should be some socially accepted age limit, for bringing opposite sex children into locker rooms, and bathrooms. Don't know of any places that have set those yet, in the US.
I have seen fathers with their children, maybe 6-7, male or female in the locker room, with him, and sometimes they ask the most embarrassing questions, for parents, but they are children, and don't know, or understand sexuality!
They know mommy and daddy have different parts, but when they see others, and their 'parts' are bigger, or maybe, uh, it's more punishment on the parent, for bringing them in there, that situation!!
But what can they do, sometimes? Does the club have a child care place, while the single parent showers or changes?