[bryony]

I'd be very surprised if changing genes could restructure a skeleton. Even if it were developed, you'd still need significant surgery to deal with the skeletal problems. You can grind off the brow ridges, but how to reduce the width of shoulders, size of rib cage? I can't think that the hip bones would grow, though I suppose that's possible. You can't reduce the skull size, as I should think the brain grows to fill it. So the proportions will still be all wrong.

As for testicles changing to ovaries, maybe, but how would a womb grow? It's certainly the stuff of Science Fiction.... the Tleilaxu Face Dancers from Dune managed it, I think.

I think the best bet is stopping puberty for every kid until they know what they are, but that's probably impractical!

B.