Surface extrusion with gradient from attractor Line

Hi there, 

I have a set of surfaces that extrude by certain amounts from an attractor curve. I want these to have finished gradients. I can only achieve this by first using grasshopper to extrude the surfaces then having to create an intersecting surface using the top centre points of the baked geometry to create this gradient. Is there anyone who knows how to do this all in grasshopper. I have attached shown my process of work in the rhino file, but I would love to see peoples suggestions on how to script the whole process?

Many thanks in advance, 

Tom