Three.js how to combine multiple materials with onBeforeCompile

Questions
1

Say i have something like:

//some chunks i want to override for functionality FOO
const myNormalChunks = {
   beginnormal_vertex,
   defaultnormal_vertex, 
   normalmap_pars_fragment,
}

//a version of `MeshStandardMaterial` that does FOO instead of default 
class StandardMaterialWithFOO extends THREE.MeshStandardMaterial{
  constructor(params){
    super(params)

    this.onBeforeCompile = shader=> { /*replace chunks by name*/ }
  }
}

Now i can use the FOO version of the material. But what if i want to add another version of the MeshStandardMaterial that does both FOO and BAR?

const BAR_onBeforeCompile = shader => { 
  /* 1. replace another chunk */
  /* 2. add something after beginnormal_vertex */
}


class ShaderMaterialWithFOOandBAR extends StandardMaterialWithFOO {
  constructor(params){
    super(params)
    this.onBeforeCompile = /* ??? */
  }
}
  1. i’m kinda thinking it is possible through some hacking to pipe these callbacks
  2. this wouldn’t work though, because there is no #include <some_chunk> after the first onBeforeCompile processes it, and i have no way of knowing what it got replaced with.

The only thing i can think of tackling this is by having some super global like GLSL code with every possible permutation controlled by #ifdef? But i would prefer not to modify the THREE.ShaderChunk object globally.

someChunk = `
  #ifdef isFOO 
    /* logic */
  #endif

  #ifdef isBAR
    /* logic */
  #endif
`

^ this seems somewhat tedious and prone to error though.

Also having something like:

const mySuperUberOneSizeFitAllOnBeforeCompile = shader =>{
  if( isBAR ) {...}
  if( isFOO ) {...}
}

Does not work because three.js has a caching mechanism that ignores these conditions. Say if I had 10 materials using this same callback, they would all compile as a single one, randomly selected from that list.

Any advice, ideas?