I've visited 5 or 6 of those countries but never more than 2 in the same trip. Travel between them is close to impossible and it would take a year to make that trip without hubbing in AKL. If flying you are looking at about $20k for discount economy non-resident fares to all those destinations. The old CO (now UA) island hopper is the easiest/cheapest way, but also goes to the "worst" of the destinations (the bottom half). You need to work out your time/money/objectives balance as this is not the same as backpacking in land areas.