Let me say it this way: The real problem is that we are ignorant of many facets of our existence and we can, by rapidly progressing with replacements of organs, etc., accidentally ruin parts of it because we will be, when the first prototype is done, ignorant, both the prototype and the scientists, that something is wrong, though I believe there will be some indications that there is a problem regardless, though it might not be enough, tragically, for many atheistic people who don't believe in a tangible soul.
But I don't think wings, longer lives, etc. would probably be so problematic, the genome would stay the same at it's core, the organs would stay the same, etc. The only difference would be by addition or by leaving away some parts of the cells, etc. Substraction is the real challenge.
All in all, though, I don't share the pessimism of those transhumanist scientists. I don't think we are just machines and thus there must be caution. Not superstition, but caution.