I would like to introduce to you Eclipse WTP/XML Search https://github.com/angelozerr/eclipse-wtp-xml-search and perhaps you could be interested with this project.

Eclipse WTP/XML Search provides : 

 * an XML Search engine dialog (see https://github.com/angelozerr/eclipse-wtp-xml-search/wiki/Installation-Guide#first-search) . You can use Search/XML and type a XPath to retrieve XML files by XPath.

 * extension point to manage custom completion, hover, hyperlink, validator and Ctrl+Shift+G for XML descriptor.

The basic idea about extension point is to declare your references from your XML nodes and to other thing (other XML node, Java class, resource, other....) and after you benefit from  completion, hover, hyperlink, validator and Ctrl+Shift+G directly.

I had developped several uses of WTP/XML Search for : 

 * Web XML.

 * Jetty XML descriptors: https://github.com/angelozerr/eclipse-wtp-xml-search/wiki/XML-Jetty-Plugins

 * Struts2 XML descriptors : https://github.com/angelozerr/eclipse-wtp-xml-search/wiki/Struts2-IDE

In my case, I use WTP/XML Search since 2010 in my professional project where there are complex cases. I tell you that because I think WTP/XML Search is mature.

Liferay IDE is integrating WTP/XML Search, so perhaps you could be interested too. I had create a long time a bug https://bugs.eclipse.org/bugs/show_bug.cgi?id=330576 to contribute to WTP.

Hope you will like it.

Regards Angelo