Is it a red flag if the justification for my research (why it is likely to matter) is popularly sourced? I want to write a paper on a certain specific topic (it's not terribly important what it is, this is intended to be a generic question). I can find sufficient peer-reviewed sources to provide a foundation for much of what I want to synthesize, but I'm coming up short when it comes to establishing a justification for my paper - that is, why it matters now, why someone would care to read it or use what I hope to find. What I can, find, however, are popular writings - newspaper articles, blog posts, random mentions in chat rooms, etc. saying something like "oh, I wish we could accomplish Specific Goal X under Conditions Y! Here's how it would help me/us/Bill/those guys down the street/etc.". I'm not seeing that in the literature - papers about X don't seem to cover using it under Y, and papers about Y don't seem to consider how it would affect X.

Is it reasonable to set up the justification for a paper by citing primarily popular (non-peer-reviewed) works (as long as I have a proper peer-reviewed foundation for how X and Y work), or is this more likely a red flag, indicating that I lack a sufficient foundation to study this right now (i.e. either I would have been able to find sources specifically about the theoretical utility of future research into X under Y, or the very fact that there are no sources indicates that there is actually little or no likelihood that X under Y would mean much)?
Research need not be completely inward looking: a snake eating its own tail. All applied research, in fact, is rooted in real world concerns. The fact that the questions have been little studied in the past is not a reason to avoid them in the future. 

In fact, "its interesting" is enough of a justification for a lot of research, whether theoretical or applied. 

And having a potential application immediately may make it more interesting, actually.