Also your layer scheme is not going to make animation any faster. When people use multiple layers for animation they are splitting up the moving parts over several layers. Like if you wanted the head to nod, you would have the head on a different layer then the shoulders. But you are just splitting up the shadows and lines on different layers, unless you want to animate him changing colors or his outlining there is really no point in doing that.
Sure, splitting out absolutely every element to its own layer would make animation slower, not faster, but a happy medium would make things more efficient overall. Painting shadows is one thing, but animating them is a different beast. If you look at traditional (ie. cel-type) animation, shadows are almost always done with a mask layer because of how much of a pain it is to try to go back and fix the animation on a flattened, composited image. Personally, I wouldn't split the different moving parts of a single character onto multiple layers b/c it's faster for me to block things in traditionally. Heck, if I were doing some serious animation, I'd do it all in pencil on paper so I could roll the drawings and nail down the movement, then scan, downrez, and clean up, because it gives me a greater degree of precision and control of the motion before the pixel stage, regardless of the "extra" work.
I agree with Helm's take of not focusing on whether or not the process is helping the image instead of if it's pixel art. Part of my goal is to be able to internalize the process, but for my own understanding, I want to break it into its constituent parts to see how they interact with each other. One of the reasons I decided to start doing pixel art is because it gives me a chance to develop my painting skills in a smaller, more controlled environment where I can more closely examine how light and colors interact.
I find the suggestion that what I'm doing isn't considered pixel art because of my use of layer techniques somewhat shortsighted. I was under the impression that pixel art was defined by the conscious and precise planning of where and how the image is put together, pixel-by-pixel; that's exactly what I've done here. I don't see why pixel art and so called "digital art" (which I think pixel art could be considered a sub-set of) cannot inform and enrich each other. I think the adherence to purely traditional techniques certainly has its place, but to limit the definition of pixel art to those techniques has the potential to cause the form to stagnate by discouraging people from experimenting with new or different methodologies.