Power BI designer should integrate Power Map design experience, don't let Power Map just like a stand-along part of Power BI...
The ability to layer is necessary. Even if limited to some "out of the box" layers initially where Microsoft controls the polygons and allows us to reference them would be a step in the right direction. Perhaps you could initially provide the various polygons provided by the Census Bureau for the US - States, Counties, Zips, Census Tracts, Census Tract Blocks. Even if we could pass in a geographic region and Power BI map that layer while allowing us to pass in an array of longitude and latitudes to map as a layer, it would be an improvement.
