I'm not telling that small is beautiful. In maritime SAR it isn't, mainly because small helicopters don't take much fuel, which is crucial. I see the 10-11 ton class a sweet spot for those kinds of operations... not really accidental ones, but more of a purpose built machines - for example, take the S-92, throw on it enlarged sponsons with bigger fuel tanks (MH-53E style) trading some speed and power for more time on station, and you may have a nice SAR platform.
How long does it take to winch up a person ? 30 seconds, depends on hover hight and load - that's a minute a cycle. Not a lot time to save from by going faster. In scenario where you have to pick people off the water, there is actually no time to safe on that, as the rescue swimmer (if you have one !) needs some time to go for a casualty, bring it back, prep for lift, and go for another one. And I don't think putting two of them in the water will be a good move either
And two winches simply don't work together in weather.
What I think is you just need a helicopter that have the range, and speed to get there fast, and enough fuel till bingo to lift as many people it can hold. In the mean time another should be in the way to continue, where the first left off
And that still solves only a case of less than 40 casualty scenarios. Above that you can't go without a boat, it's just impossible.
If anyone would like to lift 700ppl of a ship using only helicopters, even 50nm off the shore, even using 3 Chinooks, each fitted with two winches, picking off the deck, in perfect weather, you still need about 9 hours to complete the evacuation. on the other hand, it would take probably less than two hours with another ship nearby - though passengers would be out of harms way in mater of minutes. Put those people in the water and rafts, throw some weather, and the difference becomes even bigger.
If anything - SAR operators should get big and FAST vessels to cope with that kind of emergency, not messing with helicopters making them heavier and more costly to run by giving them capabilities that will never make the difference anyway.
So my take on this: Want to improve scenario with 15 people ? - Give more fuel for more time on station. Want to improve 700ppl scenario - look for other ships, helicopters wont do much there by themselves.
BTW those big baskets - should work great in good weather when attached on scene and going short distances between casualties and rescue vessel. Throw some weather to the equation, and they become useless - just a giant sea anchor with people banging on the walls inside with every wave... not where I would like to be