I was just going to mention that: given economies of scale custom babies will probably share a lot of identical prefab genetic blocks for every specification si

I was just going to mention that: given economies of scale custom babies will probably share a lot of identical prefab genetic blocks for every specification since it would be far cheaper than engineering every trait from scratch. At that point there would be enough GM humans walking around that a virus might evolve to attack only them, and it would spread like wildfire among the population given the lack of genetic variation, the only exception being old regular humans and maybe a few of those with parents wealthy enough to get them tailor-made without any of the preexisting "parts" that the majority uses.