There already are some ferry companies in Europe that will not carry EV's and hybrids due to the fire hazard.
The P&O Pioneer (and its soon to enter service sister ship) all electric ferry between Dover, England and Calais, France has many EV chargers on the car deck in 3 different flavours, so clearly they aren't concerned. Not only to have the EVs on board but also to charge them. The ship has no propellers or rudders but has 4 360 degree individually turnable jet pods (1 at each corner) so no need for bow thrusters, propellers or rudders. It is designed to recharge during dock time at either end but because neither Dover nor Calais has the required infrastructure yet uses a diesel engine to charge the ship's batteries for the moment. When they can plug in at both sides they will remove the diesel engine and put in more batteries for a faster turnaround.
The ships I was on this week, Stena Britannica and Stena Hollandica, which go between Hook of Holland, Netherlands and Harwich, England, have a spot on the reservation to indicate type of fuel - petrol/diesel/full EV/Hybrid - but they are by no means excluded.
Irv, which ferry companies ban them?