It would be great to implement the CityGML file format. It is an open standard exchange file format for 3D features widely used in urban planning and GIS softwares.
It is used in professional 3D GIS such as CityEngine by ESRI and QGIS 3.
Rhino 3D can use CityGML files and datas with the RhinoTerrain/RhinoCity extensions widely used by urban planners and city councils.
Adding such a feature to FormZ would make it possible to create FormZ built-in solutions equivalent to RhinoTerrain/RhinoCity.
https://www.citygml.org
https://en.wikipedia.org/wiki/CityGML
http://blog.rhino3d.com/search/label/CityGML
https://www.rhinoterrain.com/en/products-1.html