Is there a extension point for CMD Line Rational Build Agent Build Def

Using a JBE build Def I can extend it and add my custom properties(generic) which are hidden from the user. The values are created dynamically during Request Build dialog processing.
I'm attempting to use the cmdline Build Agent vs a JBE, but I do not see a way to extend the Build def as with the JBE so I can define generic properties.
For JBE I use the following:
<plugin>
   <extension
         point="com.ibm.team.build.common.buildConfigurationElements">
      <buildConfigurationElement
            id="com.ibm.sdwb.zbuild.rtc.common.library.definition" buildPhase="BUILD"
            description= "Configuration for a zBuild using the Cmd Line Build Agent"
            name="zBuildLibrary">
              <genericProperty
                       genericEditAllowed="false"
                       name="com.ibm.sdwb.zbuild.rtc.common.host.server"
                       description="Hostname"
                       required="false"
                       defaultValue=""/>
     </buildConfigurationElement>
   </extension>
   <extension
         point="com.ibm.team.build.common.buildDefinitionTemplates">
      <buildDefinitionTemplate
            id="com.ibm.sdwb.zbuild.rtc.common.library.definitions"
            name="zBuild - Library">
         <buildConfigurationElement id="com.ibm.team.build.general"/>
         <buildConfigurationElement id="com.ibm.team.build.schedule"/>
         <buildConfigurationElement id="com.ibm.team.build.properties"/>
         <buildConfigurationElement id="com.ibm.sdwb.zbuild.rtc.common.library.definition"/>
      </buildDefinitionTemplate>
   </extension>

I can add the build agent cmdline tab via          <buildConfigurationElement id="com.ibm.rational.buildforge.buildagent.cmdline"/>
BUT because the extension is for a JBE it will not be accepted for a Build Agent Engine. An error is indicated when you attempt to associate the build def with the engine, which makes sense.

So is there a similar extension point for the Build Agent? Or is there another way to programatically add properties to the Build def during Request Build...

Regards,
-Steve