When BrindaPeliduck had the route there were a few major issues not related to aircraft size.
Despite the best efforts of the people on the ground and in the aircraft, company policies dictated poor cutomer service outcomes - no refunds, no sympathy, no goodwill.
The Slots went against them - people would drive 2 hours to Tamworth to get the early flight. Added bonus: if the Metro or the J32 broke, there was little backup but if Qlink broke down you could just wait 3 hours for the next one.
The regulated world we live in prevents businesses like airlines from reacting to market conditions. Unable to vary schedules/slots to match your markets, unable to quickly change fleets to respond to fluctuations in demand, 6 months to get a complex type on your AOC, applications assesed by CASA weenies who have never done the thing they are assessing.
....could go on and on...
September is the target, Inshallah.