China cannot retaliate against every single country who sends its top level officials to visit Taiwan. If Pelosi landed in Taiwan, next time will be the PM of Japan, President of EU, head of NATO, VP of US ............. etc. etc. etc.
So China need to address the root cause of the issue, which is Taiwan. None of these people will come if Taiwan does not invite them. Taiwan must realize there are consequences that will cost them dearly.
One way is to reclaim one offshore island of Taiwan each time it happens. It is not quite reunification, and it leaves the burden on Taiwan and other country who send their VIP on how to respond.