So I want to define when the control goes back to the calling application. I basically want to remove the message from the queue as soon as the process instance has started. Are there any other posibilities to achieve this other than inserting a "fake" short waitstate right after the start-node?
No you don't, just add an async attribute to the first automatic activity in your process definition. So for example if the first activity is a service task, add it there.
