Best way to swap shaders from custom GUI

I'm creating a Ghost shader that has an option to write to Z buffer on the first pass then color on second pass. Option is set in custom shader GUI.

1. Can someone confirm there's no way to enable/disable shader passes? I don't think you can but want to make sure.

2. I did a test and I can swap shader files in the custom GUI which effectually enables/disables passes (one shader has a pass, the other doesn't). Any drawbacks to this approach?

3. For 2 to work, the separate shader's ShaderLab properties need to be the same. Is there any way to include an external shared block of shaderLab properties?

TNKS!

G