We have the same need. I have tried to create a data source that connects the activity to the employee master and then to the org model.
Using the employee responsible to connect to the employee master then the org unit from the employee master to the org unit.
If we can build a combined data base or joined then I think you can accomplish what you are looking for.
Any insight on how to make this work? I have read all the documentation I can find and can not get it to work.