I can see that doing a manual, exploded deployment will allow modification of property files. The fact that the CLI and web interface does not cater for this type of deployment makes me think that this is not really encouraged. This is also risky since future deployments of the same artifact could unintentially over-write property settings. Ideally the property files should be seperate from deployments. Is there a way to do this?
Finally decided to use the "user.home" system property of the VM and place user property files relative to this.