GPU Shader Hardware Requirements Question
This pipeline doesn't map triangles, but looks at each vertex in isolation, so it cannot do more than draw a wireframe.

You can probably color these pixels differently by inserting a block between the line generator and the frame buffer that, for each pair of coordinates received, runs a small program/state machine that decides what value to write to the framebuffer.

At this point however all 3D information is lost already (the line generator doesn't interpolate Z values, even though it could probably be extended to do so with little extra cost).

For useful shaders, you probably also want to reverse the rotation (so the shader has access to world coordinates), which requires another matrix multiplication block or a separate state.

For lighting, we need to run triangles rather than vertices through the pipeline so we can determine the normal vector (which would be underspecified otherwise), which is a considerable change, but should still be possible with the existing framework.

The other thing that is missing in the current pipeline is a Z buffer.