As others have said,
Upgrade bids on MH only attract tier points and Avios for the original fare booked.
The only benefit is the experience on board which is nice of you have an A330 from MEL to KUL, if your upgraded sector is to DAC on the morning departure you could end up on a 738 and that business class is a very minimal difference with economy.
Lounge access you had anyway, as a BAEC Gold you can access 1st class lounges and I think in MEL the QF F lounge access will be nice. (J fare only gives you business class lounge access). If you have no status on QF you miss the F lounge.
Globalist