Geometries are low-level and deep in Cesium so they only know about their topology.  KML will be much higher-level in Cesium and built on [data sources](https://github.com/AnalyticalGraphicsInc/cesium/pull/750) (CC @mramato).  For now, I would suggest moving these functions into a separate branch or even your app.  As we start work on client-side KML, we will be happy to collaborate and reference them.