(That is, wait for Him to perform a healing in the mind of the TS that will remove his or her desire to change sex.)
It seems to me that this is essentially the same question that comes up in any other healing. Some sects believe it's wrong to seek medical help for someone's medical problem; instead, we should rely on God to heal His way - which is assumed to mean miraculously.
Most Christians, of course, reject that idea. Can God perform miracles of healing? Certainly. Does He? Of course. Is such healing better and more perfect healing than any treatment medical science can offer? Absolutely. Should we pray for it? Definitely. And should we therefore avoid doing what we can as humans to help the ill? Absolutely NOT.
We fully expect that sometimes God will involve us in His works. We expect that our actions of mercy are part of His plan. We honor doctors. We volunteer at hospitals and mental health clinics. We don't just pray that problems will disappear; we commit ourselves to whatever we can do to help. Like the Samaritan who washed and bound the wounds of the robbed man, we know that God's will is for us to do whatever we can to help the suffering.
God's way of healing is whatever works. We already know this; we already believe this. For some reason, we have a "Let God do it" theology that applies ONLY to transsexualism. Nobody wants to stand before Christ and hear Him say, "I was hungry, and you said you'd pray for me but refused me food; I was thirsty, and you said you'd pray for me but refused me drink..." Yet, for some reason, we seem willing to risk "I was suffering, and you said you'd pray for me but denied me the help that was available."
If we want to stand in the way of mercy, let's at least not use God's name as we do so.