ClassNotFoundException: com.sun.xml.messaging.saaj.soap.SOAPDocumentImpl

Issue

We're trying to deploy a legacy application which has several web service related libraries packaged with it. In order to minimize the effort to run this app under EAP 6 we've disabled the web-service module via jboss-deployment-structure.xml:

<jboss-deployment-structure xmlns="urn:jboss:deployment-structure:1.2">
  <deployment>
    <exclude-subsystems>
      <subsystem name="webservices"/>
    </exclude-subsystems>
  </deployment>
</jboss-deployment-structure>

However, if the container loads the legacy application before other web services, we get:

java.lang.ClassNotFoundException: com.sun.xml.messaging.saaj.soap.SOAPDocumentImpl

Have we made incorrect assumptions or misconfigured the legacy project's deployment?