that will be costly for sure, but sovereignty isn't negotiable. As for blocking arms reaching Taiwan, send in warships to patrol near Taiwan and check every ship like they do to NK.

IMO, actually even if Taiwan hasn't declare independence, China need to seriously consider of containing Taiwan. Things have change, and I think it is pretty safe to say that majority of taiwanese aren't interested in returning to motherland at this point. One way to do that is to contain Taiwan economically. By forcing foreign businesses to abandon Taiwan if they want to keep doing business in China. That will hit Taiwan economy deeply. As for taiwanese businesses in China, the same treatment must be apply to them, they must move their entire businesses to China if they want to continue doing business in China. I believe that if you want to tame a stubborn beast, you need to starve them first.