Would you argue that a transwoman in a society that practiced FGM or footbinding or forced marriage should undergo those things because it would reinforce her femaleness?
I might.
To be honest, I'm dubious about the premise that mutilation is good treatment. But an otherwise-healthy adult making informed choices about their body under the guidance of a competent mental health practitioner?
I think forced marriage would probably be a moot point. The kinds of societies that have that practice don't seem like the kind of societies interested in forcing a dude who thinks he's a chick into marriage with another dude. Especially if we're talking about adults making informed decisions. Those kinds of societies mostly seem interested in forced marriages of prepubescent girls. Far from me having to counsel against it, the transwoman would be hard pressed to find anyone interested in playing along in the first place.
And if they did find someone interested in playing along, it wouldn't really be forced, would it? Can you imagine?
"Congratulations! We found the one guy in all of Yemen who wants to marry a former dude. So you have to marry him whether you like it or not."
"Thank Allah! Now I can finally feel like a real woman!"
As for FGM, think about what this entails. You've got a guy who, in order to feel more like a woman -
- is surgically removing his penis and testes, and then
- is surgically replacing them with a reasonable facsimile of a clitoris and vagina and so forth, and then
- is surgically removing or altering those new features;
All in the service of more closely approximating their self-image of a woman in that culture. At what point in the process is he going over the edge from treatment to harm?
And as long as we're talking about adults making informed decisions, foot binding is probably just another question of surgical treatment. Binding is most effective at a young age, while the foot is still growing. For someone whose mental health depends on closer conformity to that social goal (right or wrong), foot surgery to get their feet closer to the "bound" result might be indicated. I don't know. But since sex reassignment surgery is already on the table, I'm not going to write off other possible mutilation-as-treatment options.
If we had unisex bathrooms then the choice of bathrooms wouldn't exist, and therefore wouldn't be required to make anybody feel any sex at all. My compromise of having an uncategorized bathroom available to anyone allows a non-sexual choice. Using it wouldn't boost a transwoman's womanliness, true, but neither would it detract from it. A neutral outcome, what could be a better compromise?
That's not a compromise. It's a non sequitur. A compromise seeks to solve a problem by satisficing between competing goods. Your third bathroom ignores the problem entirely.