Fewmiles, that is an interesting analysis that you did there. It seems clear that you have more time on your hands than I do.
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A few of the assumptions that you made are of course, as you say, fantasy. Particularly the one where you assume that all pax automatically purchase the lowest fare. Many travellers, not well represented on this bullitin board, do not do this, because they are busy business people who need the flexibility that the full fare offers. Our travel policy states that all restricted, non refundable fares are to be refused. If this is not done, and a change needs to occur, the employee is liable in principle if not in practice. Also, we would refuse to fulfill the Saturday night stay requirement. Hence, we do not book the cheap seats.
The changes in the upgrade policies do not bother me - it just means that I, as a full fare paying passenger, will have more access to the upgrade now I am not competing with those that have the really cheap fares. I do think though, that upgrades at the gate should still be possible from any fare.
It would be an interesting analysis to see who generates more revenue for the airline - an 40,000 Qmile traveller like myself paying full fare, or a 100,000 Qmile traveller who only ever pays a bargain basement fare.