How to dynamically change TaskOwner/PotentialOwners of a task in jBPM5 ?

Issue

The requirement is to assign users to tasks before and during a task execution.

Specifically:

• Is it a good idea to assign tasks to variables, eg. 'node1User', and then assign the users as a map, eg. (node1User=John, node2User=Paul, node3User=George, node4User=Ringo). If not, what the recommend approach to assign users to tasks before an instance is started?

• Is it possible to assign a different user to a task once a instance has already started? It is understandable that users will only be able to assign new users to tasks that haven't been executed yet.