Taiwan in reality has been an independent country, with its own political (democratic) and economic (private, capitalistic) systems, military, legal system, foreign policy, its passport is recognized by most countries and actually its citizens can travel to most countries without a visa. China cannot be a democracy because of Taiwan is simply a pathetic excuse. Actually it is just the opposite. Taiwan has proposed one country with a GOOD system in response to one country with two systems. The reason the government does not want faster pace of democratization is that the party does not want to lose it's absolute power. Party over country.
S. Korea is in much dire situation facing N. Korea, that does not prevent it from adopting the democratic system, and the results, in contrast to its compatriots in the north, is astonishing.