I understand your concerns about demonology, though I would say that by the 15th century it was already well established in European grimoires. And I agree that maintaining a connection to the official Vancian structure of the game is a good idea.
I am from Portugal, actually. Crazily, many medieval-born grimoires slash magic books are still sold in general use here, like the Book of St. Cyprian, which I think everybody outside the big cities knows. LOL.