the debug switches are passed to the surefire plugin via the -DargLine=-Xdebug...... property.
However when user defines the argLine parameter for surefire plugin in the pom, the system property is not being evaluated.
There's currently no solution to the problem. One idea that needs some prottyping is to add a method to the embedder that would be able to run the build on top of MavenProject instance instead of a pom file. That we we could dynamically inject the additional debug switches dynamicaly when constructing the MavenProject instance.