is it really helpful for the proficiency and currency of a pilot to do all kinds of support work (instructive and character-building as it may be) without flying an aeroplane for several months?
It may not help currency. But that isn't the point of the exercise. The person is being assessed by his/her potential future colleagues in terms of their ability to fit in with the ethos of the operation. It is in effect an elongated interview. That's exactly what's happening with the 'rampies' at Buffalo air. I for one would have clambered over hot coals or more appropriately thin ice to get a chance to be a Rampie with Buffalo.
Many smaller operators, skydive outfits, smaller flying schools etc operate on a similar principle. They can't have passengers or glory boys or personalities that clash with their collegues. That's how I got my first flying job. I kept turning up with my smiling face until they got fed up and let me loose on one of their aeroplanes. When the the other pilot left I moved into his job. The pilot who followed me got the same treatment. But others came and went despite them saying they would 'do anything to fly with us'. Apparently turning up regularly and mucking in wasn't one of things they would do. Fail!
Looking at the first series of Ice Pilots there was a character who typified the problem. He bitched a lot and wondered why people were passing him by. Disappeared by the second series unsurprisingly.
Sorts out the Skygods from the pilots.