I’m trying to create the equivalent of custom render passes. For example, an Albedo pass (replaces all Diffuse and SSS shaders with emission shaders and sets volume shaders to 0 density), a more advanced Normal pass (normal pass, except it accounts for both bump maps and normals through indirect Glossy / Transmission).
I can either have it do this within the materials themselves automatically (probably harder than it’s worth)
-OR-
offset all faces’ material index by n (input in the render-layer?) during the render. This sounds easier than the first option, and also probably allows for much more flexibility and custom render-passes designed by the artist.