Re: South Pacific chartering
I can only comment on Thailand. Spent a lot of time there yet did only one short charter. It's hard to beat the cost, culture, beauty, infrastructure, entertainment, and diversity of friendly people.
The weather can be nice and as well, or it could rain every day, depending on the season, but you probably knew that already.
The downside is the you might not find the selection of boats found in more popular charter destinations.