You can OLCI but it doesn't print you a BP, it only prints a 'you're checked in, please proceed to umm check-in, to get your boarding pass'.
And as a side note, why drive to the airport? If there's that many of you, meet at Southern Cross and cab it (then you can all drink as well, else what's the point of an F Lounge run
).
The only certain way to get BP's seems to be if you're doing a QF/JQ combo, in which case, the QP will spit out the day-return SYD-MEL BP. Every time i've tried to get my BP for SYD-MEL at MEL for JQ35 i've been told 'can't do it'. That's at the QP, the J lounge, the QF check-in desks, the QF F Check-in and the JQ Check in and the JQ service desk (although i've heard reports to the contrary, i've never been able to).
For those of you doing JQ36 up, are you able to simply use the transit area at SYD to avoid going out and back again, and get your BP in between? Just curious