If it's only teachers, admins and course creators that need to "retake" lessons, they can always do that through the "edit" function, even if you have "no retakes" set. They're not really retaking the lesson per se, but they can see (and edit) the pages and questions, and isn't that what they really want anyway? I don't know why you would want teachers / admins / course creators to actually retake a lesson in the same way that a student does.
As for my problem, it doesn't seem to matter whether there is grading or not, Moodle still forces the user to answer every question every time a question page is encountered, before it will allow you to proceed to the next page. And, since I have ~20 courses, each in 3-5 languages, creating (and maintaining) an entirely duplicate set of courses just isn't practical. But thanks for the idea.