If JQi has a list of 'when things go wrong at X time in MEL, which flight do we scrub?' my suggestion is it's JQ7 and the return JQ8.
It makes sense as in theory there are three options to managing displaced pax - JQ43/42, QF35/36 and QF37/38. It used be very common for JQ pax to be moved onto QF, or even EK back when they operated the route. Anecdotally though now it seems less likely to happen and even like today, downgauging to A321 and doing a fuel stop in DRW is an option when everything is running fairly full.
