FWIW I don't actually think it's impossible to have spaces that are nude, mixed sex and safe and respectful.
I think it's perfectly possible and would actually be a good thing for the nudity and privacy of both sexes to be less fetished. I just think it's impossible in our current culture.
So if that's where we as a society want to get to, the honest way to deal with it is to tackle the male behaviours that mean we need single sex spaces then get rid of single sex spaces.
What I can't get behind is this idea we should start by letting male bodies into female spaces and magicaly all their pre-existing male socialisation goes away and there will be no problems.