Etihad may be skewing the calculation in their favour, but it seems to me you are trying to make several skews the other way. First off: your contract was with Bestjet, not with the airline. Second, there simply was no business class on the flight you had booked - you were offered an alternative routing and presumably could have had your ticket refunded. Instead, you chose to fly on the metal available. Third, you are claiming some kind of hardship - but you would simply have had a slightly narrower seat and had to endure 50 minutes with only one drink to tide you over between lounges. Fourth, you are claiming that the lounge access is not relevant because you have status and could have accessed the lounge anyway, but this is nevertheless a significant element of the business class product.
We have all had to "endure" short connecting flights in economy on inter-continental itineraries and it isn't a deal breaker. When there is no J, there is no J.
Maybe you do have a moral entitlement to a small amount of compensation to make up for your disappointment, but your expectations are unrealistic. Think in terms of a bottle of wine or a very few thousand points. More than that sounds like DYKWIA.
Some of your points are fundamentally wrong, and I disagree with others:
1. Bestjet are the issuing agent for the ticket, but I would argue that the contract ultimately resides with Etihad as the airline that is delivering the service. They have fulfilled their end of the bargain by ticketing the flight as requested, and I don't see how they can realistically be responsible for VA cancelling the booked flight because of a shortage of aircrew - 3 remaining flights needed to go that evening; one to SYD and 2 to MEL but with only enough crew for 2 planes, so they cancelled the first MEL flight so that one flight operated to each destination. Looks very much like a VA or EY problem to me.......
2. You mentioned "We have all had to "endure" short connecting flights in economy on inter-continental itineraries and it isn't a deal breaker. When there is no J, there is no J". If you'd read the full thread, you would have seen that, as stated in the original post and several times subsequently, there WAS business class on the flight I originally booked. This flight was cancelled and I was downgraded in the lounge as the subsequent flight (which was the only remaining flight that would get me to MEL in time for my international flight) was an economy-only aircraft.....
3. I was flying to the UK for Xmas to visit family - to say "I could have had my ticket refunded" (and therefore not travel) is ridiculous.......
4. I am NOT claiming hardship - as stated SEVERAL TIMES, my point is that I didn't get the business class leg that I paid for, and am being denied any kind of compensation because VA's procedure is to issue a fully-flexible economy ticket for the new flight and Etihad are claiming that a fully-flexible economy ticket costs more, so they don't owe me anything......
5. A significant proportion of people flying business class would probably have status-based lounge access anyway. This will undoubtedly be factored into the cost calculations made by every airline. Stand-alone single-entry lounge access
Given that I WAS booked into Business for that leg, I don't see how you can believe that an expectation of compensation is unrealistic?
I don't have any DYKWIA issues - my point was, and remains, that I didn't get the service I paid for and Etihad are using deliberately-unfair calculations to avoid compensation, which pi$$es me off to the point where I don't see why I should just drop it. As noted extensively on this forum, Qantas use similar highly-dubious standard procedures of downgrading to a fully-flexible economy ticket, and then using the price of that fully-flexible economy ticket when calculating compensation. If everyone just shrugs, they'll continue to get away with it......