The final step (barring any overlooked missing bits, requested refactors, and of course, rolling in dependencies already submitted as PRs) consists of:

renderPrePassMgr.cpp related:
A) shifting .addFeature( MFT_XYZ); calls from ProcessedShaderMaterial::_determineFeatures to ProcessedPrePassMaterial::_determineFeatures
B) mimicking the "// set the XXX if different" entries from RenderMeshMgr::render in RenderPrePassMgr::render
C) fleshing out ProcessedPrePassMaterial::getNumStages() so that it shares a 1:1 correlation with ProcessedShaderMaterial::getNumStages()
D) causing inline void Swizzle<T, mapLength>::ToBuffer( void *destination, const void *source, const dsize_t size )  to silently fail rather than fatally assert if a source or destination buffer is not yet ready to be filled. (support for #customTarget scripted render targets)

Reflections:
A) removing reflectRenderState.disableAdvancedLightingBins(true); entries. this would otherwise early out from prepass and provide no color data whatsoever.
B) removing the fd.features.addFeature( MFT_ForwardShading ); entry forcing all materials to be forward lit when reflected.
C) 2 things best described bluntly as working hacks:
C1) when reflected, a scattersky is rotated PI along it's z then x axis in order to draw properly.
C2) along similar lines, in terraincellmaterial, we shut off culling if it's a prepass material.

Skies: scattersky is given a pair of rotations for reflection purposes, all sky objects are given a z value for depth testing.

Engine/source/renderInstance/renderBinManager.cpp

@@ -36,7 +36,8 @@ RenderBinManager::RenderBinManager( const RenderInstType& ritype, F32 renderOrde
    mRenderInstType( ritype ),
    mRenderOrder( renderOrder ),
    mProcessAddOrder( processAddOrder ),
-   mRenderPass( NULL )
+   mRenderPass( NULL ),
+   mBasicOnly ( false )
 {
    VECTOR_SET_ASSOCIATION( mElementList );
    mElementList.reserve( 2048 );
@@ -60,6 +61,9 @@ void RenderBinManager::initPersistFields()
    addField("processAddOrder", TypeF32, Offset(mProcessAddOrder, RenderBinManager),
       "Defines the order for adding instances in relation to other bins." );
 
+   addField( "basicOnly", TypeBool, Offset(mBasicOnly, RenderBinManager),
+      "Limites the render bin to basic lighting only." );
+
    Parent::initPersistFields();
 }