@CantThinkOfACleverOne
OK, that does seem like a workable arrangement - though expensive.
Something like this should be front and centre of GC feminists' position on this issue, shouldn't it? Maybe with a name for the policy ("equitable toilets" - whatever). So that we don't appear to be just saying "no men in women's toilets", but instead we have a put forward an arrangement that would best cater for everyone's needs (other that transwomen demanding access to women's toilets as some kind of validation), while preserving women-only facilities.
At the moment the GC position (or at least the way it gets presented, even on here) seems too easily misrepresented to the wider public by TRAs as being bigoted.
I'm not sure whether you are new to this debate, but what you suggest as the best, most widely acceptable solution has been proposed by every single grassroots women's rights group and by every individual women's rights campaigner active on this issue. Myself included.
This solution is generally known as "third spaces" and we have not only proposed this solution, we have offered to campaign for third spaces alongside the trans community. Privately. Publicly. On social media. On our websites. On Tv, radio and the press.
This has been explicitly rejected by trans rights activists as transphobic, exclusionary, regressive and discriminatory.
Even though trans rights organisations are much better funded than disability rights ones - so well funded in fact, they could simply pay directly for the necessary building work - they have chosen not to spend a single penny on alternative, mixed-sex provision. Not on campaigning for it. Not on funding it.
The only reason some places now have a third space in addition to female-only and male-only spaces is because the people in charge understood that single-sex provision continues to be necessary even though trans rights organisations demanded that those should be abolished.
The reason why we many of us are now simply say no to males in female spaces, is because the end goal is not in fact accommodation alongside single-sex provisions, but the complete abolition of single-sex provision altogether.
(This long explanation does not take away from those who point out that if males who identify as trans are unsafe in male spaces that is a problem for males to sort out amongst themselves. Women and girls are not human shields for vulnerable males.)