There are easily implementable solutions that will improve safety without alienating customers like this solution would. Providing a proper safe charging box is probably the "simplest" as they could just buy a single item, install it, and problem solved. It might not be the cheapest, but I think alienating customers will cost more than this would after you count lost bookings. Installing such safety gear could be a selling point in advertisements as people become more aware of the risks.why cant the boats ban all battery charging after evening meal-say 6pm (before people retire to their cabins) and force people to bring a second batch of batteries to charge up during the day and/or a fire proof charging station.
There's probably 10 other ways to skin that cat that don't involve turning customers into adversaries.