Thanks for an interesting article.
I think that the point about something being 'natural' or not requires careful distinction. In the philosophical sense of the word the 'nature' of something refers to its 'essence' or what it 'really is'. In this sense the 'natural' development of a human being refers to that development which is proper to human beings, if they are not somehow disturbed.
The examples you quote of starvation and illness are in this context disturbances of natural development. This is also a convincing justification for us to apply medicine: it restores the development to its normal – natural – course. The same reasoning would also lead to a condemnation of techniques that lead to the 'enhancement' of humans as unnatural.
With regard to the technique of producing sperm cells from adult cells and using that to create a baby in a test tube – this clearly has nothing to do with the natural way of human procreation. I understand the noble ideal of helping people to have children – but in morality, the end has never justified the means. So do scientists really want to be involved in a technique that distorts the natural way in which humans procreate, and 'play God' – as you put it? Or should we focus our attention on ways to assist procreation that are respectful of the nature of human beings?