It would be nice to have more control on how the global transforms are loaded and applied. For example, there is no way to avoid the GrabAnnotationTransformation to be applied even if you forbid it through the use of a (Security) CompilerCustomizer.
According to Cédric Champeau it is not that trivial because the Global Transforms process is tightly hardwired with the compilation process. The only (ugly) workaround is to override the Groovy classloader.
It should be nice if you could specify a sort of "blacklist" of GlobalTransforms that has to be ignored during the compilation phase.
Ideally, it should be possible to do this with a Compiler Customization.