In most Java EE servlet containers, there seems to be a different method for setting deployment-specific variables. (And it is a pain to learn it or re-learn it for each container type ... Tomcat 'Catalina config', Weblogic DeployPlan.xml variables, Websphere... etc).
Why not set up Aviarc to look for a value set in aviarc.engine.aviarcData, and use it if it exists, but fall back to /var/aviarc/aviarc-data/ if a value is not found. (Or have a mechanism for 'No aviarcData setting... Checking /var/aviarc/.... checking /var/opt/aviarc/... ')
That way, if you are happy enough to install Aviarc in /var/aviarc/ then the aviarc.war can be started in any servlet container with no further effort in understanding how variables are set.
[Noting that in Windows, the path C:/var/aviarc/ seems to be callable with just /var/aviarc/ ... at least in Windows 7.]