@WhiteFire
I can see what you mean, but wouldn't the regrets of changes to the body be represented by detransition rates? I've also seen those programs with detransition-ers but, as it currently stands (and has stood for a long time), the UK's detransition rate is very low (anywhere from 0.5% to 5%).
Even if we were to assume the upper limit of 5%, that's still not that serious when you consider that:
1). The majority of medical detransitions in the UK (typically the stopping of HRT) aren't even about the individual realising they aren't trans. Amongst detransitions in the UK, most of the reasons given by people are that they haven't been accepted, have been physically or verbally attacked or threatened while transitioning, or haven't achieved as substantial a change as they feel comfortable with and would therefore like to return back to looking (at least) suitably like one sex instead of looking like androgynous/in the middle.
Also, if you go to trans forums, there isn't really any denialism that I've seen about the fact that people might not get what they want out of transitioning.
As for prison - I mean, they're prisons. I imagine everybody in them doesn't get amazing treatment.
I'm not trying to minimise any potential weirdness that could come from mixed sex prisons, but what are the big concerns? Sexual assault? Because I'm pretty sure that women sexually assault women in prison anyway (a lot more cis women than trans women), just like male-on-male sex abuse in prisons.
Idk, but I seem to recall seeing some official figures reported a while ago about mixed sex prison spaces (or trans-inclusive prison spaces, however you want to say it), which showed that sexual assault from trans women was lower than would realistically be expected for a prison setting. In fact, I think half of all incidents were done by the same person (who had been imprisoned for sexual assault on the first place). That doesn' sound like a bad decision because they were trans, that just sounds like bad judgement to keep them with other prisoners at all...