To be honest without a live show probably more than any version Big Brother Australia could survive without a "host" if "Big Brother" himself was implemented in the same way as previously. It's also worth remembering that in the North American format the host only really interacts with the houseguests in three ways - to reveal twist and to oversee the eviction and HoH process, and in all three "Big Brother" could perform that role.
I don't think it would be the right call to drop the host, and I suspect any host will take on the role of narrator too if the show is pre-recorded, but if any version could survive without one it probably is BB Australia.