I know it's not in the Greater Polynesia region but Micronesia was Spanish for quite a while before selling it to the Germans. If you avert the Spanish-American War, then maybe Spain might keep the area even after potentially decolonizing the Philippines. If you somehow manage to make Spain take over Panama (again), which would be super hard due to the Monroe Doctrine and Panama potentially needing notable autonomy to even accept Spanish ownership, it'd be much easier for Spain to reach their Pacific possessions (by the way, keeping Puerto Rico and/or Cuba also help in this scenario, of course).