Can I construct my own Packet_OUT and deliver it to destination switch "out-of-band“?
Yes, one can add a new component by setting priority greater than the path planner component (pathplanner has priority value set to 15, new component should have priority set to 14) which instruct the controller sends PACKET_IN notification to this new component before pathplaner. This new component then can send PACKET_OUT and instruct the controller to stop notifying other component about the arrival for PACKET_IN. For more information on adding a new component please refer "OpenFlow Controller" chapter in the release notes. (Note: it is also possible to disable pathplanner.)