If one of the packages specified (action, model, or test) in the seam-gen setup script is the default package (empty package), then all of the packages must be the default package. Java does not allow classes in the default package to be imported into classes that are not in the default package. Allowing this situation will lead to a project that cannot compile.
The validation I would like to have put in place is that if one package uses the default, then they all have to use the default.
For instance, the following would be illegal
This validation would happen during the validate-project target.