As mentioned in 2.2, it is highly desirable that your build produces the same deployable unit (ie. Mule or Web application depending on your deployment model) for all target environments. This is made possible by the externalization of all the configuration variables in properties files.
If the use of external overrides is not an option for you and you have to create different deployable units for your different environments, avoid manual operations at all cost. A good approach is to use a different Maven profile for each of your environments in order to control the build in a strict and reproducible manner.