rgoer, I did exactly that and my map wouldn't compile!
And my shader had exactly one definition in it to redefine a "metalsteps" texture. Of course, I am willing to accept that I may have made a mistake, so I will try again.
Unless... I only add in the altered shaderlist file and the shader when I go to test and remove it when I compile?
I'll be back with more when I've tried all this out.