From what I see in the WildFly server code, system property replacement in the content of the permissions.xml file isn't supported.
I am having similar issues in WildFly 11.0.0_Final to set read file permissions via permissions.xml, I am not able to set paths for read permissions in permissions.xml. Tried all options - hard-coding exact path, relative path with env. variable, only <<ALL FILES>> seems to be working. I have enabled debug in standalone-full.xml
and copied exact permission name and class in the permissions.xml but did not work for me...
Can you please update if it is fixed in WF11? or we need to resort to <<ALL FILES>>