Hi Maciej,
Glad to hear that you will work on this issue. This will be a big important feature in jBPM-4.5.
Here is some requirements that I met.
1.need retrieve sub process instance and super process instance relationship from history
2.need know the starter of a process instance
3.retrive task name from history task. refer: https://jira.jboss.org/browse/JBPM-2896
4.need query all of history tasks of a process instance.
Cheers.