The difference between China' spectacular growth and Russia's economic stagnation has much to do with Russia's lack of a large overseas community with business skills. Chinese leaders might respond that they have learned from the Cultural Revolution, and would never repeat such a mistake. And yet fallible human beings always find new mistakes to make. For example, Americans long have condemned the Salem Witch Hysteria of 1692. An independent Taiwan is an insurance policy for China, to speed recovery from any future maladies.
Large countries have their own unique capabilities and advantages.
Nor should political independence mean a hostile military orientation. Americans, for example, coexist happily with an independent Canada, but would violently oppose the military entry of an unfriendly Great Power. China has the military power to wreck Taiwan's economy and starve them into surrender. By analogy, examine Germany's options in 1848-1900. With an educated, skilled, and rapidly growing population, Germany was poised to lead Europe.