Yeah it would be a great middle step tool.  Use standard Vue interface to import/export, work up your textures, basic placement of items, creation of terrains etc.  Then once everything is in, then you activated this kind of "Live Vue" program and work with it like it shows in the video. 

Edit the mountains like that would be awesome, esp the cave making.   Real time lighting / shadows would be awesome for replacement of items and trees.  So in the "Live Vue" you can set all that stuff, set motion paths(ie actually drive the vehicle to set the path if desired), and do other changes.  You could even play it back and edit cameras in real time.  Then when you are done you go back into non live version of deep quality rendering.

Thinking it is about time technology is ready to make this a reality.  But you have to take advantage of the modern video cards to do it.