As for whether preserving fertility (banking sperm or eggs) before starting hormones (as teens or adults) is a worthwhile tradeoff on an individual level, that's a choice for an individual to make. In no circumstances is it not abuse to force more of natal hormones into a trans person already harmed by them.
This idea that the trans-identifying have the 'wrong hormones' and all that is essentially just a cult-like religious belief.
Looking at it from a perspective grounded in material biological reality: they desire to be the opposite sex, which isn't possible, so instead take hormone-altering drugs in an attempt to mimic some of the secondary sex characteristics that develop naturally on individuals of the opposite sex.
That's it, no magical thinking required.
The suggestion I'm making is therapeutic - it is supportive of the biology of the person who is suffering with a unbalanced hormones. At the end of the treatment I propose, it remains a possibility that the person can live a normal life, being able to reproduce etc - as opposed to becoming sterilised.