In a scenario where this tech works as well as we are dreaming of and has generalized in hundreds of millions of buildings: isn't there a risk of a general weakening of our immunity systems, making us? 

Basic logic behind this question: certain/many classes of virus eradicated from many modern buildings => our bodies are generally less prepared to encounter it in other settings => the day the setting changes, we are especially vulnerable.

(epistemic status: I'm very ignorant in these fields)

Your next question seems like a crucial point to me. Bed nets are imperfect but since mosquitos can feed on on other animals, I suppose mosquito populations don't disappear when entire regions use bednets more often, they just slowly become less malaria-infected.

Very enthusiastic about this project, which I agree can fill an important gap in the learning journey. I will follow with great interest!

I think it would be relatively simple to replicate for languages other than English in the future. (after this passes beta phase, of course!)