Hi Rinne,
While trying to find out out what else could be done for exception handling in jBPM 4, I came across this article: http://www.schabell.org/2009/12/custom-jbpm-exception-framework-for.html. It talks about the exception framework, though implemented in jBPM 3.2.
We could come up with something similar using this concept for jBPM 4.x.
Hope this helps you & me. :)
Puneet