If we're going by modern migrations, then here is one: The Taiping rebels head to a certain island down south...
The Sacred Republic (formerly Heavenly Kingdom) of Papua
After the failure of the Taiping Rebellion in 1864, Hong Xuanjiao manages to survive and with the death of her brother and her nephew, she becomes the leader of the Taiping. She decides to have her group cut their losses and they instead begin a plan to settle a new land... New Guinea. They begin taking stolen ships over across over to the island. Due to the lackluster Dutch presence on the island, they would begin settling and making prominent settlements. To ensure peace, they would likely cut a deal over with the Dutch. After all, the island didn't have much value to the Dutch at the time and thus the settlement would over on the top half primarily. This would cut off the Germans from trying to go and lay a claim on part of the island and before long, the British would get involved.
The Hong Dynasty cuts a deal over with the British to get some further stability and focus on growing themselves over in the region. Perhaps if they are lucky, they may be able to claim the whole island for themselves. British and Dutch are happy to try and get some resources from it and letting the Hong Dynasty serve as the middle-man. Over time, the Chinese refugees begin mixing in with more and more of the Papuan indigenous peoples. As the faith tries to stabilize, it takes in more and more of influnces, such as in becoming a state church like Anglicanisn. Born on a combination of Protestantism, some bits of Anglicanism, Chinese Confucianism and Papuan folk religion, this would be the foundation over for the Heavenly Kingdom. They'd likely be isolationist to a degree, focusing on settling and building up on the island along with remaining together as a whole nation, using faith and their hostile surrounding to remain together and not splinter, though they will federalize and delegate power.
They remain pretty closed off during World War 1, focusing mainly on gradually modernizing over time bit by bit and gradually their own cohesive identity. Hong Xuanjiao's legacy begins settling in such as her commanding and trainng of female warriors, which would play an influence over on the island as the cultures mix and Chinese becomes the unifying language on the island, though influence by the language. The Heavenly Kingdom Church also becomes stabilizing more, with Hong Xiuquan getting some sort of sainthood or holy reverence along with the various other heroes and the like, including Xuanjiao.
However, they would become likely involved over in World War 2 as the Japanese attempt their invasion of the Dutch Indies. The Dutch call upon them for aid and they do so though with the promise of Dutch and British assistance in modernizing. Despite them lagging behind, their numbers and training in reinforcing the the forces earn them some victories and they play a part over in the Pacific theater. All while reaping the benefits of assistance and investment from the Allies. By the end, they are beginning to grow more and more with outside investment and modern political movements. Perhaps the island becomes a spot for Chinese refugees while Christian democracy becomes a dominant force on the island in terms of culture and development. Despite this, they still focus a fair it over on self-reliance and growing. Likely undergoing some social movements regarding the indigenous peoples there and the like. The nation would survive the Cold War and into the new millenuim, known for its weird history and background along with rising issues such as environmentalism.
The Sacred Republic of Papua is now a federal parliamentary republic as the legacy of Hong Xiuquan becomes cultural and the state church with a prominent influence. Major politicla parties would be Christian democracy, social democracy and maybe a Christian socialist one given the protocommunist ideals of the Taiping Rebellion. Regarding
Social Progress Index, GDP and HDI, I would say that at worst, they're just above Malaysia and at best... just below Chile or Argentina.