Try fake global illumination example?
EDIT: This is probably the best way for the flat colors effect your trying to get, just adjust light angles at certain angles.
kind of, but the big issue is that ground plane angle is typically such that it gets heavy ao applied too, so the ground becomes dark, which I imagine you don't want. Will look a bit more over time, but definitely don't count on it. Of course an alternative is to use the flat lighting ACEs on 3DObjects directly.