[Pharo-project] About Adding/modifying in SUnit or not?

Hi all, I am working on pushing environments in SystemNavigation. SystemNavigationTest previously used ClassFactoryForTestCase from SUnit for generating classes. Now I need an environment-aware ClassFactoryForTestCase. Should I directly modify ClassFactoryForTestCase since a class generator should now be environment aware? Should I subclass ClassFactoryForTestCase and put it in SUnit? Should I never changed SUnit and put it elsewhere? ;-) #Luc