I imagine they would use a different name for Shiastan. Besides Stans being used to name areas farther to the east usually, I dint believe it was thought common to be used back then, at least not by the French. Please we called Shias Shiites in the US until halfway through the occupation of Iraq, so I imagine they had an even less accurate name for the group back then. Plus, isn't this area half Sunni? Given how the area is almost entirely between the Tigris and Euphrates, Mesopotamia has never been a better choice of names.