OK, will wait.
Do you think it is also possible to redefine (somehow) how candidate group and candidate user assignment is perfomed?
I will explain - in Activti it is possible to use candidate group or candidate user. Most interesting is candidate group.
I'm currently doing integration with Liferay - and using candidate group alreay allow to assign task to some "Global" role in Liferay - for example to Site Admin.
But, in Liferay most business processes are performed in context of some "group" - Organization or Community. Each group has own roles (like Community Administrator or Organization Owner) and of course user may ave different roles in different groups.
If I will able to "redefine" or "override" standard assignment behavior, in this case it will be possible to use standard BPMN 2.0 sepantic (candidate group) but assign it to specific groups (in this case group will store both - information about group id in liferay and role).
I saw implementation of UserTask class - but looks like it is not supported any handlers, so, I did not found any way to customize this logic. If it is possible - I may create task in the JIRA.