A lot of our users will be those coming in through a VM or ZeroClient (think Citrix) session. In our testing we haven't even been able to get the Cesium "Hello World" test to work. Is there a way in which we could use Cesium for these customers? If it helps, we are only interested in ever using 2D representation (map, not globe) of Earth.
Do the systems support WebGL? Can you post the output of http://webglreport.com/
Does Cesium throw an exception? Is there a message in the console?
You could consider using TerriaJS, which uses Cesium for 3D when it is supported, and falls back to 2D (based on Leaflet) when Cesium can’t run due to lack of WebGL support.
But if you’re only interested in 2D, why not just stick to a 2D map like Leaflet or OpenLayers?