I have a solution.

1. make shader forge great.

2. make lots of cash out of it.

3. get hired by unity.

4. fix their shaders.

:D

Built in Unity shader with white color, when not lit, will be the same as the render setting ambient color.

In the same situation SF shader will appear darker.

Flat white diffuse.

Maybe this will help you https://dl.dropboxusercontent.com/u/99714/Unity%20Projects/Shader%20Forge/Screenshots/progress_day15_time_browser_filter.jpg

It's a little complex but it works for now.

Very nice!

Seem to be able to do that in 0.06b, complete?