Oh, but this could well prove interesting to the general public!
@FaustoDeMartini 's gripes are valid, and we old V-Ray users may have a bit too much ease in the “translation” from old Max, enough to make it sound nonsense to newcomers (of V-Ray. I wouldn’t dare, Fausto. ^^).
As joconnel and Vlado well said, your go-to material is the VRayBlend shader.
VRayBlend is a multi-layer, maskable, stochastic and multi-operation shader.
It can have up to 10 layers (base + 9 coats. Recursive if one so wishes, with a blend into a blend, into a blend…).
It’s maskable, as all layers (but the base one) can have a mask determining their influence on the result.
It’s stochastic in sampling, so that adding layers will not add computation time in a linear fashion: three or six layers take the same amount to be sampled (crucially, not to render! that will depend on the materials in each layer, of course.).
It’s Multi-operation, as a single checkbox will make it a mix, or an add, between layers.
So, back to your initial questions:
*) Top-Bottom Shader:
V-Ray Blend at defaults, your two materials into the base and layer one, layer one has a Falloff map as mask, set up as shown (it’s really two clicks. Unfortunately there is no maxscript access to shading curves’ points, so this can’t be scripted. I’d love to be corrected on this.).
Notice that you could add as many top and bottom shaders inside either the same VRayBlend (using the other layers) or in a recursive fashion, with a blend for the top and a blend for the bottom layers, and so on.
Further, notice you now have the whole latitude of the falloff map to choose what the reference, and direction/type of the blend should be.
Last but not least, it’s trivial to save a simple setup in a material library for rapid re-use (again, i know of no scripting access to key parts of the shader, on the Max side, or i’d script you one.).
It being this simple to setup means it’s unlikely we’ll get it as a separate shader. There’s always OSL, but i suck at it and can’t quite find love enough for it to get over the few obstacles, so others may be more helpful there.
*) Shellac shader:
This is simpler still: your carbon fiber weave shader as a base material, and your reflective coat(s!) in the layers above it (below, in the VRayBlend UI. it reads top down.).
The only little trick is to tick the box which says “Additive (Shellac) mode”.
You may choose to use a Fresnel term in the shader itself, or in the blend map (fresnel falloff).
I’d suggest using the VRayMtl fresnel approximation for better results.
As for any wholly additive shader, it’s down to the user to ensure energy preservation (in other words, no sum of shader components should go above 1.0, or it would emit more energy than that which hit it).
For a carbon fiber with a clearcoat, the Specular may be the component at risk of going above 1.0, so f.e., you can set the specular for the weave at 25% gray, and that for the coat at 75% gray, and that would work.
This stuff can be scripted, with the caveat of maps, so i’d still go for a material library save of a preset.
Here too you’re not limited to one coat layer, which should have you cartwheel in joy the second you’ll start playing with the Blend. ^^
