How to enable property substitution in deployment descriptors in EAP 6/7/8?

Issue

• How to enable property substitution (property replacement) in deployment descriptor in EAP 6 or 7?
• Can property substitution be used in ejb-jar.xml, for example:

       <enterprise-beans>
          <message-driven>
             <ejb-name>...</ejb-name>
             <ejb-class>...</ejb-class>
             <activation-config>
                ...(snip)...
                <activation-config-property>                    
                   <activation-config-property-name>maxSession</activation-config-property-name>                    
                   <activation-config-property-value>${my.prop.config}</activation-config-property-value>
                </activation-config-property>
                ...(snip)...
             </activation-config>
          </message-driven>
       </enterprise-beans>

and then pass system properties at start-up via command line (e.g, -Dmy.prop.config=20) or via a properties file (e.g. -P myprops.properties) which contains name=value pairs.

• In web.xml files, system-properties could be defined using ${} form (such as ${property}, set using -Dproperty=xyz and also could be set in the JBoss profile, but the value is not being expanded in the web.xml

 <system-properties>
        <property name="property" value="test"/>
 </system-properties>

• Is it possible to change the context-root at deploy-time for a web-application in a given EAR file that includes an application.xml file, without changing the EAR file?
• We are porting application from EAP 5.1.2 to EAP 6.2.0 in testing, observe org.apache.naming.resources.FileDirContext.setDocBase() does not support property substitution in EAP 6. Got the following error:

JBWEB000235: Allocate exception for servlet webdav: java.lang.IllegalArgumentException: JBWEB006706: Document base /opt/testapp/userAA/bin/${userAA.testapp.directory} does not exist or is not a readable directory
        at org.apache.naming.resources.FileDirContext.setDocBase(FileDirContext.java:147)

• How to use dynamic values in the web.xml file ?
• How to refer environment variables and/or system properties in web.xml
• JAVA_OPTS defined variable foo=/somedir. Folder ${foo}/bar exists and got read-write permission for the application. In 6.4, the war file deployed fine. In EAP 7.2, war file deployed failed with error ${foo}/bar does not refer to a valid directory