A wide river would be easy enough already. Its just water. We have water. Make long, long canyon full of water using the terrain editor.
The water has to be drawn in the individual textures. Its not like you can define zero altitude as being water... is it? It seems that this was the problem with the shore lines in general. It took HTC quite some time to impliment them.
Granted.. once rivers are in place, bridges would be next

Functional bridges that would do things like support a tank, or block spawning in a certain direction if destroyed.
Is there a development roadmap?
I'm sure HTC is waiting to finish 1.06 before deciding what they are going to do next. "Wew.. 1.06 is done.. what do we do now HT?"
AKDejaVu