You can imagine an infinite set of negative consequences of practically any action --- your choice of breakfast cereal, via a chain of consequences, might cause

You can imagine an infinite set of negative consequences of practically any action --- your choice of breakfast cereal, via a chain of consequences, might cause the end of the world. Still, we make choices, because we have to terminate the chain of hypothetical situations at some point, using the heuristic that without a specific reason to believe that some effect happens, it doesn't. With respect to the topic under discussion: absent any particular reason to suppose that this kind of gene editing causes your hypothetical wartime probability difference or your hypothetical 1% fertility drop, there's no reason to use the possibility of these effects to ban the treatment, since there's as much reason to believe you're making these things less likely as reason to believe that you're making these things more likely. Regarding changes being advantages: do you really believe, deep down, that being weak is just as useful as being strong? That being resistant to disease is just as good as being vulnerable? That being dumb is just as good as being a genius? Give me a break: I can't seriously entertain the idea that we don't know which traits we'd want our children to have, given a choice.