On answering a question that no one has asked
Well, this is the core of research: You ask questions due to your knowledge and expertise that others probably cannot ask. And then you publish your results. There is no general need to justify the question as long as your question makes sense. It will be sufficient if you describe how you arrived at that question. You certainly have read some literature for that, so you will also cite some sources. 

And reviewers will be happy with it if your methods are fine, your results are plausible etc.