Why discuss potential scenario, when history can provide many that already happened ?
For example, from my backyard:
14th January 1993 - 4 o clock in the morning, 6-meter waves, 100kts wind, 2°C water, "MF Hewelius" ferry ship with 64 people on board capsizes. Ship on German waters, helicopter SAR units respond - Dutch, German and Polish, plus German rescue vessel "Arcona". All 3 Polish long range rescue helos ready for take off - can get there faster, but didn't get the green light, soon two becoming damaged on shutdown in high wind. One fly after being apparent that German Seakings can't get there on time. On scene Dutch and German Sea Kings don't have rescue swimmers, can rescue only few people that could be strapped on by other survivors in rafts ('Marine Electric' rings a bell ?). One raft with 3 survivors in immersion suits is capsized by rescue sling from one of the Seakings - all die of suffocation. Arcona vessel on scene can't do much good either. Polish helicopter with rescue swimmer gets on scene to late to pick up anyone alive, is collecting bodies, the process is continued for another two days.
Out off 64, almost all got out of the ship, 9 persons are rescued - those who survived 4 hours in water, 10 others were never found.
From my searches on this types of accidents, the number of people on board is not a major factor, you can't and shouldn't consider preparing a helicopter for picking up 24+ people, it's not efficient. What's the most important, is to have a good decision making system, good coverage with as many types of rescue systems as possible, and their speed is a major factor.
Even if you take a Chinook with 3 winches, you won't be as efficient as having 3 smaller aircrafts, and in high sees you won't be able to use it anyway. And if something that big that have 30+ people on board goes down, it have to be hell of a storm, and it's mostly in remote areas, where you can't pick up that many people anyway because your time on station is limited by your fuel load which goes very fast in those conditions. That's why I don't find AW101 as an efficient SAR machine here - I don't think that in "SHTF" situation it will have enough fuel to fill up its cabin anyway. Cheaper, smaller Pumas, S-92s, NH-90s etc will do the job better.
BTW it is not a job for helicopters to evacuate a 700ppl cruiser - that's why they have so big and elaborate safety systems, so the people can survive on water until other big ship arrives.
Of course there are accidents like the one of "MS Estonia", also on Baltic sea, 28th September 1994, where out of 989 - only 134 survived, simply because there was no time to evacuate the ship, and no rescue aircraft could helped there.