Add/remove/update system properties in JBoss EAP 6/7

Issue

• How can I add/remove/remove all system properties with the CLI?
• Is there a replacement for properties-service.xml?
• Is there an alternative to using JAVA_OPTS for system properties?

• Tried manually removing the system property and got error

  {"JBAS014653: Composite operation failed and was rolled back. Steps that failed:
  " => {"Operation step-1" => "JBAS014803: Duplicate resource [(\"system-property\
  " => \"foo\")]"}}
  

• Can we change system properties on without a restart?