Ok. Lots of responses. I'm doing this on my phone, which is tricky, but I'll try my best.
So on one hand you say you "can understand that there may be certain spaces where still having a penis might make this more problematic/embarrassing for all involved" (how fucking dismissive you are of women's privacy and dignity) and the next you're talking about full surgery?
PS I didn't say they should be in men's spaces. I said they shouldn't be in women's. Because male.
I'm not meaning to sound dismissive about women's privacy and dignity. I'm saying that I, personally, am happy to share all MY "safe" women's spaces with a gender dysphoric transwoman (is it ok if I shorten to GDTW?) who has fully transitioned. But while I recognise that that person, in her brain, feels like a woman, while she still has a penis, that makes it a different story. For me, a GDTW walking into a woman's changing room and using a cubicle to change pre-surgery is not a problem for me. Walking in and just stripping off naked would be. Walking in and stripping off in the corner, embarrassed, with pants still on and penis still strapped down, trying to draw no attention? Christ, maybe this is my privilege again but I can't imagine how humiliating that must be. So I went for "problematic/embarrassing for all involved". Would I send her to the mens in that circumstance? Me personally - no.
And yes, the lack of perceived safety in the mens room is a men problem, and not "ours to solve", but I feel bad for those GDTW who feel like they have no spaces. So if they are respectful, and don't violate the "safety" of the space, I don't mind sharing. Note that I put "safe" in quotes due to the number of times I have been in a womens toilet that has had a bloke in it for no good reason whatsoever…
On women's prisons I agree [with the comments/extracts - haven't read the articles yet although always take DM with a bag o' salt]. Vulnerable women should not be jailed. Men and AGPs should not be in women's prisons. But I'm not saying the needs of men trump the needs of women, I'm saying the most vulnerable should be protected (generally and in law). Usually that's women, but once in a while that could be a GDTW. All I'm saying is not to rule out allowing people to consider those cases.
While it's -as you say- not my job to come up with a solution (I'm vastly underpaid if so!), I'd be happy with the law classing post-surgery GDTW as women in all respects other than anything specifically relevant to female biology and legislating generally to protect women, but allowing specific requests from pre-op GDTW for that classification to be heard on a case by case basis by a specifically appointed panel that was trusted by relevant groups and charities and included people who know a lot more about the issues than me.
Phew! Sorry for another long post - I can't seem to be succinct.