Although I already have my yearly trip planned and will not join you, I have been following kiwi mates of mine, Greg and Jean Jack with their development efforts in Tonga. I met him in Laos December 2018 at Green Climbers Home.
Their FB page is https://web.facebook.com/groups/986159234811952/
He will be able to give you a lot of information. If you are no already in contact let me know ad I will introduce you