Like with shipping any dangerous goods, including regular ICE as well as battery electric vehicles, improving the safety standards and safety protocols as problems become apparent - rather than banning the goods - seems indicated.
Probably for EV's they should be at low state of charge and batteries, including the auxilliary ones, disconnected if that is not already the case - something requiring trained staff to be sure of, which may not be the case. Not sure how that might apply to ferry type shipping, where owners travel with their own cars aboard and expect to drive away at the other end.
Appropriate fire suppression equipment seems kinda obvious - can't put out such fires but can stop the fire spreading. But I also expect improving standards to reduce EV battery fire risk is ongoing.
I note that BYD is moving to their own dedicated carrier fleet - I expect they are aware of potential fire risks in the design criteria. Given they are big in buses, trucks and other kinds of EV's, may be a contributor to electrification of shipping.