@Arcverson,
main problem is that we don't know how nature will react to this, it's true that many creature have a redundant role, mosquitoe's larva are not the only one who can filter water by exemple, but the problem is that we live in a world where bee, and many usefull and less dangerous life form slowly die because of human activity, and often because we tried to exterminate these little shit that we can't bear.
and it's not like we have already tried to exterminate those shit, but they are really resistant.
and nothing say that the mosquitoe's remplacement will be less dangereous.