A case can be made that the detention of the crew of the Hong Tai 58 constituted an act of
false kidnapping or whatever the equivalent crime is under Chinese law.
The authorities in Taipei will inevitably object, but the thing is
Beijing absolutely does not consider Taipei to be a fully, if at all lawful government with the legitimate right to arrest or detain anyone, including at sea. So Beijing can probably throw in charges of
piracy while they're at it, and whatever else that may apply under existing Chinese criminal code.
From there,
Beijing can criminally prosecute those deemed responsible or otherwise liable all the way up to Lai Ching-te should they wish.
Put up some 10 million to 1 billion RMB (~$1.4-140 million USD) bounties -- preferably
dead or
alive with broad immunity and familial resettlement thrown in -- commiserating with the seniority of each wanted defendant, and see where things go.

This might require some new legislation on the part of the NPC, but that shouldn't be an issue.
If Beijing is willing to put up an ~$140 million USD bounty on Lai, perhaps half or a quarter of that on his principal lieutenants and deputies, and less for lesser minions, there will definitely be people within Taiwan's local bureaucracy, security services, law enforcement, and military who'll consider the "opportunity," especially if they expect Trump to "sell them out" sooner or later.
In fact, don't be surprised if lesser members of the local coast guard and/or naval forces will voluntarily turn themselves in for lesser bounties, assuming they know they'll be granted full amnesty upon pledging allegiance to Beijing and testifying against their former
criminal leadership.
Not only will this thoroughly humiliate and delegitimize the authorities in Taipei, but there isn't much they can respond with, without likely over-escalating and hurting themselves in the process.
Perfect excuse to list Taiwan coastguard as terrorist and take back admin control of the sea around the island.
You know that PRC is routinely arresting and even extraditing Taiwanese more routinely than this one incident
Actually, by the One China policy, the PRC cannot intervene because technically there is no "Taiwan".
This is the same issue that arose in HK that lead to the protests. HK could not legally extradite to mainland in most cases. As such, the person that murdered the Taiwanese could not be extradited to Taiwan (which by the legal status of the PRC, is part of mainland China). If extradition was to be allowed, than it would cover all of mainland China.