All very interesting... One perspective has been touched on which is the circumstances of the individual. I'm 6 foot 4 inches (which is 1.94m), 47 years old with a body mass index at the high end of normal (ie not quite obese but one big weekend would get me there!) I would have to think very, very carefully about taking such a job for medical reasons... About a decade ago I was asked to take on a contract with economy only travel but we agreed on Premium Economy when I discussed it with the client simply because I am such a big unit - where there wasn't a PE product it was club. The question of liability for health issues arising from cramming someone into Economy is interesting, especially if the individual can show that they only ever travel in a premium cabin for personal long haul travel (which was a card I played in that particular negotiation)..
A friend is in a similar situation with a Y only travel policy. He "plays a straight bat" and books as economic a fare as possible. He knows that many of his colleagues wait to the very, very last minute to book their travel so are then able to find cheaper, indirect flights in premium cabins which they then book to save the company money - they also play the martyr card for having to spend more hours in the air flying indirectly. Not fair, but the company in question hasn't worked it out of doesn't put a high priority on the issue.
One final point is that there's economy and economy. I am starting my own business so am very cost conscious. I just flew LHR - DOH - MEL, SIN - DOH - LHR on Qatar in Y and SYD - SIN on Qantas in Y. I am BA Gold, and for 3 of the 4 flights on Qatar I got the magic X (blocked seat) next to me, which meant I had a row to myself - 2 being upstairs on an A380. Qatar's legroom is very decent anyway, so the 4th flight (where I had a blocked seat next to me until 12 hours before the flight but it obviously filled up at the last minute) was actually ok. The Qantas leg was purgatory with knees pressed hard against the seat in front for every second I spent in the seat - never again!