First, I don't know enough of the details to draw a conclusion that I think is truly informed, so trying to comment extensively under those conditions bothers me. To get around that problem, I'll try to change the situation to show my thinking or explain how I've filled in the blanks.
My first set of questions revolves around the fate of the new child. Do they allow him to grow into a regular healthy baby and live a regular healthy life? If you're asking whether I am bothered by using parts of the placenta or umbilical cord of a regular baby to benefit another child or an adult, I'm not bothered by that practice at all. A baby doesn't have any special claim to a placenta or umbilical cord after birth, and I support letting the parents donate part or all of each to improve someone else's health. The article doesn't say whether the new baby is "designed" to be healthy or whether it is designed to have horrible flaws that will cause the placenta to produce something needed by the older baby. The article says that the baby is designed to be free of certain diseases, but one can be free of diseases and still have some inherent defect that causes tremendous problems. If they have selected the new baby to have some flaw, then I object to creating anyone with serious problems just to make something needed by someone else. This practice would be a violation of the rights of the "designer" baby. Likewise, designing and producing a perfectly good baby, using something produced by that baby, and then killing it would also be a violation of its rights.
The second set of questions revolves around the idea of selection of an embryo to bring to maturity. If 75% of embryos are too flawed to produce pregnancy naturally, I don't necessarily see a problem with IVF using a selection process. In normal IVF, they are likely trying to mimic the natural process whereby some embryos implant and try to grow while others are discarded early by the woman's body. The idea of selecting for something other than likelihood of survival makes me uncomfortable in a vague way, but trying to outlaw things when I don't have a better explanation for why they are wrong makes me more uncomfortable.
One of the distinctions that I make in this area is the difference between allowing things for an individual's benefit and allowing things for some collective purpose. I think that things done on an individual level are relatively safe. Allowing a couple to use IVF to have their own child is not particularly dangerous. Putting a technology like that at the disposal of those trying to improve "mankind" collectively or advance "medical science" collectively is dangerous. A couple that investigates IVF and decides against it can stop pursuing it easily. However, when decisions are suddenly cast in light of what produces a collective good for the society, the couple may find it more difficult to change their mind about a procedure.
One thing that "bothers" me about the article is the collective overtone of allowing the procedure. Right now, the couple can make their decisions on their own. The more we experiment with "people" or any kind of genetically unique human tissue, the more likely we will encounter a situation where that decision becomes forced by others.
WFTR
Bill