But in the worst case caution could be a harmful position. So in these tech matters I think it's adaptive that we disagree, since if we were (hypothetically) both on the same ecosystem-engineering team, maybe our diverse opinions would contribute to a balanced strategy that I think can have the best chance of greatest net benefit.

Interesting point about null. How can we factor in risks like 'unknown unknowns' into null hypothesis thinking? I don't know right now. But I think one issue/limitation with null hypothesis thinking is that it is not imaginative. This makes it very applicable for assessing evidence for something. But not applicable for thinking about the unknown risks that could occur for something. Different thinking frameworks for different problems, not one-sized fits all, I think. But I think it is applicable for you to use it here to advocate your position of pushing forward unless we have evidence otherwise. My position differs in that I'm saying I think we need to be imaginative about the potential risks.

Germline altering should only be done in extreme circumstances, and I think this is one of them. Even if mosquitoes do pass on vital antibodies (why hasn't this issue already been noticed in wealthy people who have never been bit and have never consumed something that was bit?) or malaria finds a new way to spread or their absence otherwise creates some kind of butterfly effect ecosystem chaos, what's easier to do in 30 years? Artificially re-introducing safer versions of these mosquitoes / mosquito analogs / isolated antibodies back into the ecosystem and finding new treatments for pathogens, or resurrecting the millions of people who needlessly suffered and died of preventable diseases?

And also consider the chance that maybe nothing bad at all will happen if they all die off. Obviously, this is a very risky hypothesis that's nearly impossible to prove or disprove in a lab, but it's just a possibility to keep in mind. Complex systems like ecosystems are fickle. Sometimes removing a tiny piece of a system wrecks the whole thing like a Jenga tower collapsing, and sometimes removing a massive piece has almost no effect at all. Eliminating a parasite species doesn't necessarily mean there will be significant negative consequences. But of course, there absolutely could be.

As long as this technology is tested extremely carefully and applied to smaller real-world ecosystems which can be studied for years before being deployed globally, it seems like the overall best answer is to avoid the short-term death and despair and deal with future problems as they arise.

Evolution by natural selection no longer holds all the cards. Humanity has, and will continue to, supersede it and override it to achieve things that would never otherwise be possible. We don't have to cower in fear of natural processes anymore, because we can intelligently shape our world, and soon other worlds, as we see fit. We still have to understand these systems and processes to prevent externalities, but that doesn't mean we can't cautiously venture into this kind of technology. It would happen sooner or later, so why not right now?