Any chance you'd record the lectures like the 2012 iteration? Seems that the discussions are a big part of this pedagogical approach; and those are better captured through videos than notes/books. Also, the latest version of PaPL book doesn't seem to incorporate the mystery languages. Is there a plan to include them in the book?
I would love to record and publish the videos. However, the moment I do, I have essentially published the solutions to the homeworks. It's very hard to reuse them again. But mystery languages are really difficult to generate (especially with the additional constraints that we explain in the SNAPL paper), as there are only so many meaningful variations to go around. So, no.
You are very right that PAPL doesn't incorporate them at all. Part of the issue is the above. But part of it is also, now that I am getting really comfortable with this being a notable portion of my PL course, what becomes the nature of a "textbook" for such a course? I've struggled with this question before: I taught a (I think) really good software engineering course, but couldn't really can it into a book. I feel the same way about this now. But it means PAPL may end up being less a (half) PL textbook and more some other thing that is still being formed in my mind…
