Lunar,
Do you suggest by your question that one must work your way up the totem pole increment by increment?
How many BHL HP pilots did the Bell 47/R22/206 training scheme to step into the cockpit of 61's , Puma's, and other large aircraft? They seemed to fare well. The military does this as a routine.
I would quite happily train an ab-initio student on the 212 disregarding costs as an issue.
I maintain a helicopter is a helicopter...some are bigger...some faster...some carry more...some have fancier avionics...but they are all helicopters. You pull up on the lever in your left hand....and the same thing happens....you push forward on that stick in your right hand and the same thing happens...push the pedals and the same thing happens.
Each machine is different but they are all helicopters. We can make the system complex and costly...or we can go the other way and still achieve the same safety levels.
Look at the difference in the way we handle type ratings between the UK and the USA....that alone should indict the concept of "typing" helicopters. We use weight as the thresh hold for determing "type" ratings. I would suggest to you that a SPIFR EC-135 is far more sophisticated than a VFR only BV-107 used only for underslung work but the 135 does not require a type rating and the 107 does. In the UK...everything has a type rating and related "type technical" exams and checkrides done by the licensing authority. We on the other hand rely upon the operator to give differences training and checkrides except when we require the "type" rating based upon weight.
The conversion to larger more complex machines should not be based upon previous types flown but be based upon ability and other qualifying experience.
I can assure you, a pilot with a broad reach of experience in 206's will be the better risk for 212 flying than a pilot that has thousands of hours doing the same bus run out across the North Sea in a 332/225. The one will have skills the other does not. Each will be better suited for the kind of flying he has been doing as a result of that experience.
The transition to multi-engine flying is not all that complex when compared to learning the skill sets required for your average utility helicopter pilot flying 206's in moutains, deserts, offshore, ag work, and doing underslung work in all those places.
I would think nothing of hiring a well experienced 206 pilot for an offshore flying job...but not the reverse. There is a mystique (more like an Urban Myth) that suggests working for a large North Sea operator qualifies one as a helicopter pilot. I would suggest it well qualifies one for one sector of the industry.
Lord knows we proved flying 212's in hot and humid conditions in Nigeria was more difficult than flying on the North Sea. Ask your mates who did that routine and get them to describe how many aircraft got over torqued or bent while they got the grasp of 212 flying after being on the North Sea for years.