I hope you do write more, because I think the point you’re trying to make is not intuitive, and gets right at the core of the heteronormative assumptions about bathrooms and similar semi-private spaces. It deserves some really clear exposition, and you have written clearly on other related issues.

In particular, I think you’ve made a plenty good point about why a blanket no-trans policy would be a practically disabling (and dangerous) policy for many trans people.

But it is not the case that everyone is equally dangerous. Men are, both in temperament and physical capability, on average more dangerous than women.

So if you are actually asking for even a modest sacrifice to safety for non-trans women, it’s best to just ask for the sacrifice up front with an explanation for why it’s for the greater good (e.g. the alternative would be immensely unsafe for trans people — you have made that point but you have not made a clear point about whether there’s a downside); and if you’re not asking for even a modest sacrifice, it would be good to make it clear why you think there is no sacrifice whatsoever (or even an improvement).

This isn’t entirely an academic exercise. Depending on the answer, what policies make the most sense may differ. For instance, should we put more effort towards a consistent approach to gendered bathrooms, or should we mostly work towards universal availability of gender-neutral bathrooms (or, more extreme, an elimination of gendered bathrooms in favor of only gender-neutral bathrooms)?