Your experience as a Course Director adds much to this thread. My point still standing that an actual IE which entails an independent PADI examiner will be necessary for all instructor crossovers including NAUI. This is not the case with other agencies. Does NAUI require independent evaluators or can a Course Director working with an instructor or its equivalent complete the cross over for PADI instructors?
To compare we have to look at a few things
A NAUI Instructor Trainer in PADI would be a Course Director- able to run the academics portion IDC (Instructor Development Course) PADI or ITP (Instructor Training Program) in NAUI. At the end of this course in PADI you can be certified as and Assistant Instructor in NAUI its called a Associate Instructor.
A NAUI Course Director is equivalent to a PADI Instructor Examiner (IE) they can conduct the examination portion of a Instructor Program (PADI its called an IE- Instructor Exam in NAUI its called a IQP- Instructor Qualification Program)
In the PADI program the candidate is evaluated by the Course Director at the IDC and the IE during the IE. In the NAUI program during the IQP there must be NAUI Course Director and one other trained evaluator present this can be another CD or IT or a NAUI instructor who has been through a STW (Staff Training Workshop to evaluate Instructor Candidates- PADI equivalent would be IDCS).
Therefore in both programs the candidate is evaluated by a minimum of two people - in PADI the CD and IE. In the NAUI program its the IT and CD or other trained evaluator. The process is similar in both instances with the main difference if you have a local NAUI CD he can run both parts of the Crossover but still must have one other evaluator present during the testing phase.
So to answer your question can a CD by himself do a crossover - No he can not he must have at least one other trained evaluator present.