I wouldn't want to introduce any new microbes, since they can and will start being spread into other things.
Considering that complete mosquito genocide would, very unfortunately, negatively impact many ecosystems, what would be a good way to stop them from being a threat/great annoyance to humanity?
Seriously there are so many different projects involving mosquitoes going on. Here's just the first one I googled but there are at least several dozen different mosquito engineering projects going on.
https://www.npr.org/sections/goatsandsoda/2019/02/20/693735499/scientists-release-controversial-genetically-modified-mosquitoes-in-high-securitGenerally the idea is to use a gene drive to spread a gene in the target population. To give a simplified idea of how this works, it uses a system called CRISPR that they discovered in bacteria to copy genes. A copy of CRISPR can be designed to detect a specific sequence of DNA, and replace it with a different sequence.
The real trick here is that the sequence you're inserting can contain the DNA for the entire CRIPSR system itself. So, in normal genetics you get 1 gene from the mother and one from the father. However if you get one of the genes as a CRISPR version, it can then scan the other chromosome and if the non-edited version of the gene is there, it removes it and replaces it with a copy of CRISPR plus whatever other genes you wanted as a payload.
So, a CRISPR gene drive can force its way through the population,
even if the mutation itself is detrimental to the survival of the organism. Normally genes get weeded out if they lower the survival rate of the organisms they inhabit, through survival of the fittest. However, since a CRISPR gene drive can just over-write copies of the original gene entirely, it effectively rigs the dice. So, say you had a gene for mosquitoes that causes them to attack the malaria parasite, and normally this would be a bit costly for the mosquito (slightly lower survival rate) which is why they don't do it now, then if you edited the mosquitoes with that gene and let them loose, the gene would die out in a few generations. However, if you couple that with a CRISPR gene drive, then the new gene will spread and take over, even though the affected mosquitoes themselves have slightly worse survival rates than otherwise.
Once someone has the gene drive working as intended in mosquitoes, then there are several possible ideas. One is to spread genes that prevent them carrying the malaria parasite, another is to flip the sex of all the mosquitoes to male (less eggs that way) another would be to engineer them to not like biting humans. The gene drive is really the delivery system and what it delivers is up to what we can think up.