[@Penny]I never said nature was all good (in fact I purposefully didn't because I figured you might use your above point). I said randomness is fair. But to tackle your point, drugs and vaccines are preventative to diseases to increase your chances of surviving. Changing a humans physical traits to suit your whims is simply giving control to those who shouldn't have it. 

Most people would agree that a good parent raises their kids, and a poor or overbearing parent controls them. In nearly every case (at least in western society), a parent has a responsibility for their kids life, not a domination over their kids life. Changing physical traits goes beyond the nurturing and teaching, and it simply makes the kid into another tool to suit their tastes. Yes, it's my opinion and in the end I can't prove how it would make the world worse. We'd just need to wait and see. I just cannot see what benefits it would it have other than making a kid easy on the eyes to a (likely) high maintenance parent.