Is it possible to define custom android sourceSets for certain subsets of flavors?

I have a project with 4 flavor dimensions, which is making it hard to share resources between some combinations of flavors.

FlavorA {dimension 'Dimension1'}
FlavorB {dimension 'Dimension1'}

FlavorC {dimension 'Dimension2'}
FlavorD {dimension 'Dimension2'}

FlavorE {dimension 'Dimension3'}
FlavorF {dimension 'Dimension3'}

FlavorG {dimension 'Dimension4'}
FlavorH {dimension 'Dimension4'}

In my project, I need every FlavorAFlavorC build variant to share some resource.

However, the only available source sets are in the following form:

• FlavorA
• FlavorB
• ...
• FlavorH
• FlavorAFlavorCFlavorEFlavorG
• FlavorAFlavorCFlavorEFlavorH
• FlavorAFlavorCFlavorFFlavorG
• ...

I tried having some custom folders, like a FlavorAFlavorC folder, and then in applicationVariants.all:

if(variant.name.contains('FlavorA') && variant.name.contains('FlavorC')){
    variant.mergeResourcesProvider.get().doFirst {
        android.sourceSets.debug.res.srcDirs += "src/FlavorAFlavorC/res"
        android.sourceSets.release.res.srcDirs += "src/FlavorAFlavorC/release/res"
    }
}

This solution, however, is extremely inconsistent. Upon further investigation I came to the conclusion that this inconsistency derives from setting android.nonTransitiveRClass=true on gradle.properties.

Is there a better way to share resources between certain subsets of flavors or to avoid the issue caused by the flag?