Is there already any progress here?
It would already be a big help if the classpath container that the runtime server (e.g. JBoss 6.0 Runtime) represents, allowed to attach a single source file or directory to it.
Following that, someone could 'just' extract all source code from JBoss AS for a specific release into a single directory and then attach that in one go. Obtaining this source remains a problem (especially in a single tree format), but maybe this could be obtained from the JBoss maven repository, packaged and perhaps published 'somewhere'. (since it's open source, I guess a community member could just publish this on say Google projects orso, right?)