There probably won't be more mosquitoes of the benign species if we eradicate the problem species, unless we start to farm the nice kinds of mosquitoes or something.

Given that the whole process is about farming mosquitos, producing a few extra of the nice mosquitoes might be worked into the plan for reasonable extra cost.

Replacing the bad mosquitos with nice one's is also likely to make it harder for bad mosquitos to come back because their niche is filled.