We did of course consider the theory that the Manuscript was the work of a teenager who liked to play the alchemist.  (In fact I doubt that there is any theory left that we did not consider.)  One strong piece of evidence for that theory is the hundreds of drawings of naked women, which impress the reader for their quantity but however hint at a limited  concrete experience with the topic in question.  Indeed, it seems that at first the author drew dresses over their naked bodies, and only after a few pages he got bold enough to leave them /au naturel/.  There is also a six-page fold-out with what appears to be a fantasy world spread over a handful of little islands, like those that many kids conceive and draw in their teens.

We even had a candidate for the author, a mentally ill Bohemian (Czech) prince who lived recluse in the ~1600s.  However the carbon dating of the manuscript to ~1480 ruled him out.

The problem with that theory is that the manuscript is too long, consistent, and boring in many sections -- it seems very unlikely that a teenager would keep focused on a goal for that long, and would not put more fantastic stuff in it.  But that is not strong argument, of course.