3. If the “font” has been used to make it appear to a hostile party as some foreign natural language one would not be able to understand anyway, would it be probable, that the drawings also have a stenographic [sic] purpose to make the MV appear somehow unimportant/harmless?
— Daniel, I suppose you meant “steganography” (“hidden” messages) rather than “stenography” (shorthand?)
2. If the “text” is too structured to be language, could it possibly be something else, like music or numbers? The latter has probably already been suggested.
2.1 What would contradict the theory of a roman numbering code or something that includes numbers to a great extent, e.g. chess moves?
1. Are the thinkable reasons one could have in the 15th century to hide whatever information somehow limited?
1.1 How much thread was in the relevant time-frame from the catholic church regarding unwelcome information?
1.2 How common was it to cypher military or diplomatic information?