Give them a bunch of nukes and biological weapons and after they arrive send a message to the PRC
"Just a fyi, we sent them a 100 but they only received 80. Be a real shame if Taiwanese operators had planted them in randomly selected cities on the mainland."
There's a theory that Taiwan could achieve mass destruction with just regular cruise missiles, no need for actual WMDs.
The destruction of Three Gorges Dam would kill millions of people from the resulting flood. Be a tough target and air defense would be a nightmare, but it is still within Taiwan's cruise missile range.
There's been no acknowledgement ever of this plan, but it's pretty obvious.