Use geography data directly from semantic model in map

[OldDogNewTricks]

I have geography data in a WKT text string format in some of my dimension tables.  It would be ideal to use that geography data directly from a semantic model and have them be rendered on a map.  For example, we have a concept of a sub-county which we make by melting groups of zip codes to form a single polygon per sub-county.  I have the WKT polygon data stored as text in a delta table.  I would like to be able to create the model relationships as I normally do, classify the data as a "geography" type (could be polygon, multi-polygon, point, or line) but render the polygons directly from the semantic model instead of or in addition to the reference layers.  The older version of Icon Map allowed this functionality and it was very fast as well!