Flagged Revisions has such options already in its code. Possibly not too hard to extract the relevant code and use it "stand alone" for rating purposes only if desired (or by having the flagged rev's functions disabled) on wikis that wanted it. But yes.
One box to add: "I am <a casual editor | knowledgable | very knowledgable | formally qualified> on this topic", then we can see how it's rated based on respondent's self-claimed knowledge, and what its audience is like.
Also note an interface point: to most users, "rate this item" is so familiar from other sites, that a popup is likely to be ignored as spam and may even be seen as annoying. I'd do it how FR does it -- in a small bar on the interface itself:
I totally agree about the interface. No pop-ups please, just a small tab that opens this rating plus the mini-questionnaire will do.
Also agree with the box to add about the expertise of the reader. The 'quality of demand factors' are also great to have feedback on, for example:
- This article contained everything I expected to find, judging from its subject.