Maven model classes are missing from xstream whiltelist configuration

Some legacy restlet REST resources return org.apache.maven.model classes directly, but not all classes have alias configuration or are otherwise configured with converters, and the xstream whitelist bans them from being marshaled.

Using https://user:pass@nexus.xxx.com/nexus/service/local/artifact/maven?r=snapshots&g=com.xxx&a=reporting_2.10&v=LATEST

results in a HTTP 500:

jvm 1 | 2014-04-15 17:08:04 ERROR [qtp303405156-51] admin org.sonatype.nexus.rest.NexusApplication - Unhandled exception or error intercepted
jvm 1 | com.thoughtworks.xstream.converters.ConversionException: No converter specified for class org.apache.maven.model.Dependency
jvm 1 | ---- Debugging information ----
jvm 1 | -------------------------------
jvm 1 | at com.thoughtworks.xstream.core.DefaultConverterLookup.lookupConverterForType(DefaultConverterLookup.java:61) ~[xstream-1.4.6-SONATYPE-02.jar:1.4.6-SONATYPE-02]
jvm 1 | at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:48) ~[xstream-1.4.6-SONATYPE-02.jar:1.4.6-SONATYPE-02]
jvm 1 | at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:43) ~[xstream-1.4.6-SONATYPE-02.jar:1.4.6-SONATYPE-02]