Looking at Ivan's figures, then a -300 could shift the same payload on three trips versus the -200's four trips. Further very significant savings but at the expense of frequency which could be a problem. Would've thought a Monday/Wednesday/Friday service with the -300 would be the go.
I seriously don't think Ozjet would be silly enough to take the entire commercial risk!!! According to their AOC, they do not have approval to operate RPT services to Honiara so can only operate charters. That, by its very nature, would indicate someone else is paying them (and continue to do so, hopefully, after the SAW episode) and that other party is taking the commercial risk.
As for Our Airline being "owned by most anyone else", my understanding from the hoo-hah when the airline was launched is that other island nations have been invited to take a stake in the airline - hence the name. This would dilute the Nauruan ownership and give whomever invests some direct control as against being at the mercy of a charter operation.