Seriously? would force yourself onto BA and QF MK1 J seats because of lounge access in DXB?
Sounds like cutting off your nose to spite your face.
QF will have (according to the timetable currently) 747s with MK11 skybeds MEL - SIN and A380 SYD - HKG so there are none MK1 options, just have to avoid QF81 via ADL and the other MEL -SIN flight on a A330. Then connecting to BA will be fine. I'm keen to start with BA anyway to try their system of paid upgrades often dicussed on FT.