Thanks!
This seems about as good as reasonably possible, but it does have some trade-offs that should probably be recognized.
For these trade-offs, I assume that transgender people are dealing with a legitimate and stressful personal issue. I also assume that one thing that helps them is to try to accommodate their gender self-construct as much as (reasonably) possible.
We have to draw the line somewhere, and this seems to be more or less the right place to draw it. But consider:
Requiring proof of medical transition at any stage is going to make acceptance at that stage a regressive policy. Only people who can afford the procedure can enjoy the entitlement. This is going to be hard on transpeople who can't afford the procedure.
Requiring proof of transition to enter a women's space is also going to be problematic. It upends some existing legal and social norms. If a woman in the locker room demands to see another woman's transition paperwork, is that legitimate? Is the transwoman required to produce it on demand?