In the latest version of Pax-Construct I make heavy use of other maven plugins and often need to extend them with additional features or modify their behaviour. Because plexus relies on Javadoc tags to calculate the plugin metadata, you normally can't extend mojos without having the source available locally. So I developed the 'maven-inherit-plugin' which merges the local plugin metadata with metadata from any extended plugin mojos.
http://www.ops4j.org/projects/pax/construct/maven-inherit-plugin
Here's an snippet from Pax-Construct where I extend the eclipse plugin to add improved support for OSGi bundles:

