Some more food for your thoughts:
I'm going to write the initial client as a webclient, because I have all the technology and experience required for it. And with recent advances, it can do all that is needed. Most importantly, it can correctly display an entire globe, check here:
http://openlayers.org/ol-cesium/examples/rotate.html (might have to zoom out to see it...)
Maybe in the future, if the game is successful, there will be a 3D standalone client, which would give me so many more opportunities for bringing the world alive.
