I think your solution cannot happen because those with money and tech, and who don't have a cultural squeamishness with the idea, will get the genetic engineering first. The ultrarich. Probably the Chinese, maybe others. Then it will be a case of making the rest of the world amenable to these enhanced people. Elites don't want chaos and nor do they want anyone to threaten their dominance. So a functioning, intelligent, but malleable mass will be controlled by an elite who have the tech. Just as today the average joe doesn't have access to nuclear weapons.

"I think your solution cannot happen because those with money and tech, and who don't have a cultural squeamishness with the idea, will get the genetic engineering first. The ultrarich."

In some scenarios, not in others. With embryo selection, the gain is small enough that it will not create new elite classes with high solidarity, and in iterated/synthesis scenarios, an elite could try but the core technologies are widespread now and the end result gametes are easily stolen and replicated (imagine trying to do nuclear arms control if every single atomic bomb was walking around, having kids, and regularly shed skin cells which could be turned into new atomic bombs).

That said, this is of course good reason to oppose regulation, as regulatory capture is common and we already see a lot of self-serving hypocritical behavior by elites.