A really cool idea would be a repeat function. It would save time and space on so many projects I'd imagine (especially mine).
Basically you have a input like a surface layer, a shader/function input, and integer for number of iterations. Than TG in it's infinite glory applies said shader X times to the input (or last result). This would be useful for many shaders, for example, the transform input shader. Ever iteration it applies to the last result, or input, layering up the shaders effect.
Maybe there could be three types, a "Repeat Shader", "Repeat Scalar" and "Repeat Vector"
Image for visual example