Modern thinking is that large ferry ships are made to "be their own lifeboats", with state of the art fire suppression and damage control systems that compartmentalise the ship and keep it afloat.
I agree that multiple winching from the same helicopter is probably not safe except in the most stable and low hover regimes.
The SAR-H programme has also had a brief look at human external cargo systems, which are basically a large sling load cage, certified by the FAA, to carry people. These systems can either be flown to the incident (quite low VMax) or carried on board large vessels. Providing you are near to land or have a suitable vessel to cross-deck to then rescue rates well in excess of normal winching can be achieved.