And yet it seems it would be politically very difficult to enact even a mild policy along these lines -- its proponents would surely be condemned as racists.

I guess that's true. But it can be framed otherwise. Let me demonstrate:

"In America today, minorities are often hardest hit by the widening gap between the rich and the poor and the gap between the technologically savvy and unsavvy. Besides the more abstract measure of "genomic literacy" blogged on by editors of the New York Beta Times last week, a recent disturbing study by the FDA shows that only 15% of African American mothers and 21% of Hispanic American mothers conceive via artificial insemination compared to 40% of white American mothers and 47% of Asian American mothers. Democratic house leaders have called for more generous government assistance and educational programs to help minorities take advantage of these vital services. In related news Republicans stir controversy by calling existing government support for such programs "racist and unconstitutional" in the already fraught atmosphere of last weeks "quarrelling preacher couple" viral video. In the first part of the YouTube video rev. Matthew Young called genetic enhancement an abomination unto God and "another attempt by elitists to push social engineering and sin, masked by false eugenic and evolutionary pseudo-science, unto an unwilling and pious public". The second part of the video is a youtube respond where his husband Jeffrey Young explains that while he strives to fulfil God's commandments to obey his minister, he just can't bring himself to think God would want people to live poorer and less fulling lives and so supports certain uses of reproductive technology and thinks government should make them available. Is this just another sign of the religious right becoming a house divided on the issue? Some experts say that the outdated legislation of 2019 may be repelled earlier than... "

In a very slow and overly cautious approach of just selecting the best embryo of the mix for implantation or even just picking the best sperm and egg, you would get convergence between the groups rather rapidly. Innovation is expensive, copying is cheap in such circumstances. Any genetic advantages of say Askenazi Jews, other Europeans or East Asians will be pretty cheap source of cognitive enhancement for the third world, while the First world will have to mine its talented fraction, which may have somewhat more unpleasant side effects.

The reason why I believe a very slow and overly cautious approach might be probable, is because we already have a very slow and overly cautious approach when it comes to new medical technology.