Razib Khan has a nice short story idea.
But, the logical conclusion of generations of genetic screening of particular Arab lineages is that the clans of the Persian Gulf will eventually transform themselves into clones with very low mutational load. Even if the power of screening shields these lineages from the ill effects of inbreeding (by literally yanking out all the deleterious alleles from the gene pool by discarding eggs with problematic genotypes every generation), biological uniformity is going to have problematic long term consequences when it comes to battling co-evolving pathogens. Monocultures aren’t built to last.
In any case, interesting idea for a science fiction short story. The formula would be to take a pre-modern custom (e.g., cousin marriage) and mix it with future technology, and iterate forward.