Well, it would make any Chinese move across the Strait a much greater risk.
In a calculated risk, though, could Taiwan, politically speaking, go nuclear in response to a naval blockade? Nukes would be advantageous in defending against an actual invasion and detering the Chinese from using it's nuclear weapons, but would a blockade strategy by China warrent such a response?
Taiwan using nuclear weapons in a struggle with China would be somewhat akin to Israel's Sampson option except for the near term it wouldn't have enough firepower to bring down the Chinese house. It would send Taiwan out in a blaze of glory, but would mean the end of Taiwan. Israel, though, has the internal fortitude (most likely) to use this type of weapon in such a way. Their history prepares them for this. Does Taiwan's political leadership have the same nerve to order the destruction of their own people and nation?
What I mean is a nuclear arsenal to deter China from even invading. The whole point is the status of MAD. Would china risk mutually assured destruction?