King Kalakaua of Hawaii had a pretty hair-brained idea to create a Polynesian confederation, or the Federated Empire of Oceania. It didn't work.
He succeeded in getting the King of Samoa to begrudgingly sign up, though that appears to have been from desperation as he was in the middle of a civil war and it was just prior to Samoa getting annexed by the Germans. No meaningful Hawaiian aid arrived in time. Apparently similar deals were struck with Tonga and the Gilbert Islands. Hawaii also had a claim to the Sikaians as it was gifted to Hawaii in the 1850s and I believe the crown of Samoa was offered to the Hawaiian king in the 1850s but it was turned down.
The challenge is to make a successful *Polynesian confederation. It doesn't need to be Kalakaua's crazy scheme of OTL. You'll probably need to find a great power ally interested in backing Hawaii and not wanting to annex it, like Britain or a friendly Japan.
POD is open-ended, but try and keep it in the 19th century.