Good idea indeedGood idea indeed, as long as we limit that for only a few topics which are really recurring.
We don't want to turn any frequent topic into such thing, though. The purpose of Super User is to provide feedback to individual questions, not to be a farm of "how to" questions. There are sites dedicated to such goal, like the how-to geek.
Such questions should be references of common steps to follow, but not the ultimate answer to all these questions. The purpose of such "faq" would be to post as a comment, as an initial read for the poster, and suggest him to update his question with any specific and additional details.