Ahaha, GREAT, yeah, I'm not done with the import GUI, yet, but I already hooked up color value for material amount, when you import a png. I will make a proper import GUI with parameters to choose how you want the material amount. I'm still thinking about the most possibilities in the easiest set of parameters, like a choice between FLAT, LUM, R, G, B, A, HUE and then a percentage parameter. Or actually an array of all of them, where you can dial up various percentages that will get combined. Not sure, yet. I then might even make this a standard layer effect/manipulation. 
Great post, though, Robin! 
