Having said that, the documentation does really seem to be missing a section about custom JACC providers so I went to check the TCK setup. It looks like the TCK JACC providers are bundled in a jar and this jar is being set as a resource of the org.jboss.as.security module. I'm not sure why it was done this way but I believe it should be also possible to define your own module containing the classes and then wire it to the security module as a dependency instead of a resource.

Hmmm, how would one go about doing that exactly? I think I created a module for my custom JACC provider, then set that as a dependency for the security module (since that was the place the default implementation lives), but it again did not work (class not found exceptions). Could well be the case that I did something wrong, so an example would be great.