"I'd be happy with some more access to the existing seats on a restricted fare basis, just as the Y cabin is currently sold. "

In some markets they are. Out of Europe they are by conolidators. Booked in D class, I can get QF from FRA-SYD return for £1700 ( approx AUD4600 )

"Or the ability to upgrade legs for a sensible amount.Why do operational upgrades for free if you've got pax willing to pay $ a week or so ahead."

That would be stupid of them. They do operational upgrades if necessary whereas if they started offering such a thing, people who would otherwise pay the business fare would start using this. It would become as bad as US domestic service where there is Economy Class and Upgrade Class.

Dave