This was proposed by M Robin White I believe, amongst others: that all “women” including males who claim they are women should use the communal toilets and the appalling women who didn’t want to could have a separate space.
That was entertaining; essentially agreeing that single sex women's provision and mixed sex/gender neutral was the way forward. Job's done, Bob's your uncle, end of issue.
The many complaints (this complainant among them) on MN from activists about the issues of having to use a mixed sex space while a single sex provision exists alongside have included that it's othering, 'outing', and risky for users with gender identities (shot down in this judgment in plain terms as an argument). The real crunch points have seemed to be that even though women who wish to share mixed sex facilities in the approved way will be there, those women won't do - which seems to be a combination of that:
the real bullseye in terms of what 'validation' may mean (it's a fig leaf over a great deal there) is to be in a women only single sex labelled space with women who wish a single sex space, and with no other men permitted. I suppose 'gold star toilet facilities' in the same terms as the desired 'gold star lesbians', the women who will absolutely only sleep with another woman, and so bestows the greatest 'womanhood' upon the man. The deeply desired experience a number of men with gender identities have written about. Which is in some ways understandable, but not acceptable as it uses women as merely props for the man's need while disregarding their consent or equality, or their access, including their need for actual single sex spaces.
there is, and no point pretending this elephant isn't present and multiply evidenced over years, for some men a deep need to show women who is boss and not permit an escape from the control of men and the ideology, so the mere existance of facilities that cannot be colonised and women who cannot be forced to submit or go without, is a cause for anger and action.
there is a voiced fear (again threads here where well known men with gender identities have posted) that if women are provided with single sex options, most women will choose that option. Which admits knowledge that most women do not want or like mixed sex spaces. And that the old adage about lesbians (activist in the tweets, terf in the sheets) is probably true of women in this situation too, that many who post insisting that they have no problem at all and would love to use mixed sex toilets would in fact often choose the single sex space.
At least we have reached the point of legally having the ability to prevent the shutting down and removal of single sex spaces and the insistance that they must be provided first and then other options added. And some of the more peculiar arguments have now been legally dealt with and dismissed, by the High Court.