Personally, I would love to see the Bonza model live long and prosper. I think that there is money to be made out there with some of the routes they have tapped that are being ignored by the Big Two. But what it really needs is a set of E195-E1s or A319s that are/were cheap as chips, and run them for 10-12 hours per day, plus taking cargo, holidays and any other way imaginable to generate the revenue that allows you to sell cheap base fares. Still, that wouldn't make them immune from AOGs, pilot poaching or any of the other challenges that are part and parcel of the business these days.
You've got it the wrong way round there, that's what they should be doing with the Max. New aircraft have to be run flat out to cover the fixed costs, like leases and or capital investments. Old aircraft need to be run less at higher yields to stop fuel and maintenance costs from crippling your venture, the fixed costs are less because you invested less capital, but the operating costs increase due to higher fuel burns and more frequent maintenance. If there was cargo to be carried on Bonzas routes they would carry it, so would QLink, Rex and every other freight operator that could see a profit there, but air freight also needs reliability and frequency. Then if you go a step up in cargo, you need dedicated cargo aircraft, that then needs to be filled to be profitable as well and the cycle continues. BTW Mildura was extended to allow larger aircraft to operate there, not for passenger jets, but for freight, specifically the carriage of fresh produce, where are these magic planes that the council predicted? Oh that's right its too expensive to ship oranges that way...