We had a conversation about this topic yesterday.
In fact, we asked to Arnd why there is no "ultra thin" watch in the collection. There are two answers. First of all the HW Saxonia is already rather thin. Secondly, it is not the DNA of Lange to create such watch. Because an ultra thin watch would change the shape of the case and as you underlined it, there is a sort of consistency within the whole collection.
Fr.Xavier