we know genetic diversity is beneficial from observing nature (sexual reproduction has clear evolutionary advantages that you can look into yourself if you like). yours is an interesting hypothesis, but "developing a defense" is something that we get for free from genetic diversity. we can improve our odds of survival using technology, but culling genetic diversity in favor of gene hacking compatibility comes with some tough trade-offs since you're choosing to ~always adapt manually. not to mention the ethical concerns depending on how this condition arises.