Would a large grass field make a good green screen? This is a picture of a green field that changes into a hill.

The idea is can you can have a large, organic 3D green-screen this way?



I used a program to normalize the darker green areas of the field using replace color and increasing the thresh hold without losing texture and wonder if this could be done to a live feed?
It's doable, so long as you have some time, diddling around in After Effects with the Keylight chromakey and the camera tracker... Here's an example I made a while back at 4m25,5m17, 
6m04, 8m33 (and a few other sections):