Decomposing
I answered the question about my child earlier in the thread. Basically, I hope as an adult he makes ethical choices re using women's space.
I don't consider him to be at any more risk in the men's as a transwoman than I do as an effeminate gay man, and gay men can't use women's spaces to protect themselves.
I would promote provision of private, enclosed, sink included, floor to ceiling gender neutral provision in my city, and work with him, and any trans people, on that project.
How can people self police ? By being honest with themselves. Do they really NEED Hampstead Ladies Pond, as a male person who feels themselves to be gendered 'woman', when they have a mixed pond ? Do they really NEED to try to shut down women only refuges when they could raise funds for trans refuges ? Is it any more difficult than understanding why I, a white woman, probably shouldn't barge in on an indigenous women's group and decide it should meet my needs ?
I do think allies have a lot to answer for in encouraging maladaptive ways of thinking that obscure a person's sense of reality. I'm not suggesting it is easy for people with GD. It isn't. It's bloody hard. But they are as fully human as you and me, and yes, that means we can expect them to behave as ethically as we would expect others.
I also expect men to come to the table, and work amongst themselves to solve the problem of male violence, so that gay men and transwomen aren't at any risk in male spaces. Men are also fully human, and can be expected to engage in this work.