Much as I love the old Queen Air, I can't think of a less suitable aircraft for short cycle scheduled service hauling big loads in high ambient temperatures.
At the very least they will need two spare engines and a bunch of spare cylinders on the shelf, and the expertise to change them.
Also, this is not the ideal first twin, so if they go for a low time (and you can bet low-paid) pilot, the whole thing will be yet another failure in Tonga's long history of aviation failures. Chathams was probably the closest they have ever been to a properly run air service.