How's this then:
CASA geniusses tell me that a survey equipment operator is a Task Specialist when the aircraft is on task. Fair enough and so far so good.
However, if the sensor is not operating and you are ferrying to the location, the same person is an Aerial Work Passenger.
Currently, you can do any commercial operation on a Class 2 Medical certificate providing you aren't carrying passengers. This currently includes survey, freight, Ag etc. Under Part 138 - if my Task Specialist magically turns into a passenger - do my survey pilots now need a Class 1 medical?