No way to use <moduleSet> in a multi-level project

The <moduleSet> as illustrated at http://maven.apache.org/plugins/maven-assembly-plugin/examples/multimodule/module-binary-inclusion-simple.html
assumes that all modules are directly below the pom.xml and therefore does not work in a hierarchical (multi-level) project structure.

See discussion thread: http://www.nabble.com/Assembly-and-multi-levels-multi-modules-t1747056.html