Forward3D piece(and others) as more function-like (in-out)

[hyyou]

In "Forward3D_piece_ps.glsl", the shader access global variable in a very hard-coded way.

For example Notice that the forward3D access inPs.pos directly :-

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float fSlice = log2( max( -inPs.pos.z - .... 

My wish
The Ogre's official piece should use more-local-like name e.g. forward3D_inPsPos, and the external "caller" responsible to pass it like:-

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vec3 forward3D_inPsPos=inPs.pos;  //user code
 .... insert piece "forward3dLighting" .... which use "forward3D_inPsPos" instead of "inPs.pos"
 ..... float fSlice = log2( max( -forward3D_inPsPos.z - .... 

This will promote decoupling.
If it is done, in custom HLMS implemention, I don't have to try to identify the fields the Forward3D sneakily want, and riskily rename mine to match it.

Another interpretation
It is hard to explain, so here is another attempt:-

Current pixel shader is roughly-like :-

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input: inPs
algorithm :{
     my hlms
     forward3D block (access inPs.pos)
}

I wish it to be :-

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input: inPs
algorithm :{
     my hlms
     vec3 forward3D_inPsPos = inPs.pos;       //<-- still my code
     //^--- like a parameter to a Forward3D function
     forward3D block (access forward3D_inPsPos)
}

P.S.
Many other places are also hard-coded, but I am not sure whether it should be/easy-to encapsulate :-

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float f3dMinDistance	= passBuf.f3dData.x;

^ The passBuf should probably be aliased as forward3d_passBuf before passing to forward3D block.

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vec3 tmpColour = BRDF( lightDir, viewDir, NdotV, lightDiffuse.xyz, lightSpecular );

^ Forward3D should provide forward3D_out_lightDir, forward3D_out_viewDir, forward3D_out_NdotV .... , and call a dummy BRDF_USED, and let user hook to the default BRDF it manually.

If this post is too hard to understand, please tell me, I will try even harder.
I am not sure if it is a good idea though.
Custom C++ HLMS implementation is used by just a few user anyway.