Oops sorry BB.  After re-reading your explanations a few more times, I realize I didn't get all of what you mean.  I also missed a few crucial bits in the cat fur shader.  So here's the original "non-GC" cat fur shader.

n = Noise();
n.x_Index = 4 * ImageMap("BlueSiamese.jpg");
n.y_Index = 4 * ImageMap("BlueSiamese.jpg");
n.z_Index = 4 * ImageMap("BlueSiamese.jpg");
n.min = 0.3;
n.max = 0.4;

h = Hair();
h.Root_Color = BLACK * n;
h.Tip_Color = WHITE * n;
h.Specular_Color = BLACK;
h.Highlight_Size = 0.01;
h.Root_Softness = 0.25;

s = EmptySurface().Alternate_Diffuse = BLACK * h;

s.Diffuse_Color = WHITE * ImageMap("BlueSiamese.jpg");

s.Diffuse_Value = 1.0;

Here's what I'm guessing render GC will do.

n.x_Index = 4 * AGC(ImageMap("BlueSiamese.jpg"));
n.y_Index = 4 * AGC(ImageMap("BlueSiamese.jpg"));
n.z_Index = 4 * AGC(ImageMap("BlueSiamese.jpg"));

h.Root_Color = AGC(BLACK) * n;
h.Tip_Color = AGC(WHITE) * n;
h.Specular_Color = AGC(BLACK);

s.Alternate_Diffuse = AGC(BLACK) * h;

s.Diffuse_Color = AGC(WHITE) * AGC(ImageMap("BlueSiamese.jpg"));

output = GC((s.Diffuse_Color * s.Diffuse_Value) + s.Alternate_Diffuse);

Am I correct or just totally dead wrong?