you don't have to change the default.* files inside the jbpm-gwt-console-server.war as you can simply make a copy of these files and drop them in configuration directory (for AS7 it is jboss_home/standalone/configuration), e.g. rename copied default.session.template to session.template and add your modification. Console when loading first checks if there is a custom file in config dire and if so load it instead of default ones. More on this can be found in documentation as well.
Yes, it should work as you described
HTH