Use classpath resources as fileSets

We want to do assemblies of our projects using shared assembly descriptors (http://maven.apache.org/plugins/maven-assembly-plugin/examples/sharing-descriptors.html). Also, we want to include some directories and files in the assemblies, but we want to store that particular directories and/or files inside the shared descriptor artifact JAR.
For example in our shared descriptor jar is included a file src/main/assembly/files/startup/startup.sh and we want to have the assembly generated containing that file.
Now when we execute the assembly plugin on a project using the shared descriptor, files contained inside sharedDescriptor.jar aren't copied into the assembly.

The shared assembly descriptor has a fileSet defined like this:

  	<fileSet>
  		<directory>files</directory>
  		<outputDirectory></outputDirectory>
  		<filtered>true</filtered>
  		<includes>
			<include>**/*.sh</include>
			<include>**/*.csh</include>
  		</includes>
		<fileMode>0755</fileMode>
	</fileSet>

And the *.sh and *.csh files are stored inside sharedDescriptors.jar.

We have a project "A" and "B" that use the shared descriptor. We want to include sh and csh files on the assembly of A and B but the only way to do this is that the sh and csh files are duplicated in the file structure of both projects in /files directory instead of instead of have them only one place ( at /files directory in sharedDescriptors project)

Is it possible to provide these files (*.csh, *.sh) within the shared descriptor jar?
If not, we propose extending the assembly plugin so it can have defined a FileSet in the form:

  	<fileSet>
  		<directory>classpath:/assembly/files</directory>
		...
	</fileSet>