I have about 4-5 questions like that. Usually, they are complex questions in areas where quite a small percentage of people have expertise.
There were several cases when I was wondering whether it makes sense to write a question at all, because I was almost sure that I wouldn't get any answer.
I think it makes sense to introduce such a badge to encourage people to continue writing complex questions in rare areas.
Also, I want to point out the (kind-of) similarity of this proposed badge to the "Unsung Hero" badge.