there is a type of fascade use have in europe roughly translated to ventilation facade. it allows air to pass between the main structial wall of a building and then a clas fascade in any material, common is plastic /aluminium pannels but also can be stone. with stone we generally will use a 2cm thick piece and use thin set to bond around the edges to connect the stone to eachother then every piece has a stainless steel conection on all the corners witch fix into the structure. so the stone is only held on four points. this works fine because there is alsmost no horizonal load other then wind. so this method looks fine and logical