It's true that the best place to put this in is the same xml file where the factories are defined, i.e. (standard)jboss.xml. So, jboss_6_0.dtd makes sense.
I don't like the idea of a seperate DTD for EAP though. Putting it in some other xml file and getting it later from some managed bean (which would serve just this purpose) is not nicer. IMO, a system property would be better than that.
I can't suggest anything better. So, I guess I'm gonna do the DTDs.
I won't be able to complete this earlier than Monday though. Is that ok?