It would be nice to have a feature that allow process developers/designers to define an "external" interactive application to launch in case a task is executed (a la Carnot BPM, no advertise intended). For example, I would like to deploy some JSP's in the same app server where jBPM is living, so I could execute the JSP and have access to task/process instance variables.
This way, I could have the freedom to develop my own GUI's without them worrying about the complexities of business workflow (since this would be in the process, not in the JSP); the JSP would handle the complexity of validations, access to the model, and even have access to process/tasnk instance variables!. However, there may be a problem whenever you try to release a new version of the process, or a new version of the JSP(s), since the variables shared by both of them would need to be synchronized (while designing the process and developing the JSP).
P.S. I've heard there's something like this in jBPM 3.2, but I have been unable to find it, is it in the CVS repository for public download? Under what tag/branch/trunk? (Are you there Roland? ;) )