The current ground type system provides lots of different ground types, farm, water, grass, rock, forest and more, however one important type is missing - Urban area.
I clearly understand that it isn't "just texture". And it actually should be generated with objects like buildings streets and so on. Maybe it is possible to do them similarly as trees are created today - but to make sure it does not hit FPS too much - maybe switch to bump-mapped tile over some altitude/distance.
If it could be done the way it doesn't hit FPS too much it would be great - even if the buildings are undestructible.
This way we would be able to fly over London, Berlin, Moscow and other cities that would actually be large - and the terrain would look much more realistic.