> How can it be to late to add this to the hibernate properties as any other property? It behaves like a "normal" config property, right?

No, it's an environment property.

> which is far from perfect. I would love to change that. Also, the JGroups settings are defined somewhere else. Now you are introducing yet another spot in the build which influences the test outcomes. 

No JGroups options are defined in that same systemPropertyVariables element.
Don't know what to tell you. Are you going to embark in fixing the java class definition initialization process to get rid of a single option?