Could Qing dynasty China have moved all foreign off the mainland to Taiwan. They could effectively move all foreign influence off the Taiwan allowing free trade there and let only Government ships bring in goods from there to certain mainland ports like Shanghai, Macau and Hong Kong; wouldn't that allow for greater control so when opium is realized to be detrimental and banned since only government ships bring stuff to the mainland the local Chinese traders for the most part wouldn't buy opium (granted there's the whole bribery & black market, but at least the opium would be curbed dramatically)