Hi and welcome,

To take the points I can in order.

Pilot skill was pretty much the key here, as to what percentage could have pulled it off under the same identical circumstances I think you will see a pretty tight bell curve (at least in the US pilot population, it varies a bit more across the globe) with the pilot of this flight at or near the top end of the scale. Your more typical pilot (center of the curve) would probably done nearly as well, maybe a bit harder landing, a few more injuries, a bit faster sink rate after "landing"). The other end of the scale might have broken up or flipped on impact since ditching is a very narrow margin situation. US aircrews (all airlines) are a pretty highly trained and skilled group and most are very professional and proud of their abilities. Keep in mind it was an average flight crew that did such a great job getting that crippled DC-10 into Sioux City Iowa several years ago.

Another factor was the type of aircraft involved. I am not a huge fan of Airbus planes (If it ain't Boeing, I ain't going) but the A320 series is designed for hard use (lots of cycles per day) and is reasonably sturdy. A 737 would have probably done as well while larger planes might not have fared as well. For those speculating on the effect of the water temperature, it doesn't really matter at the speed the plane was going. I am pretty sure the investigation will show the initial impact managed to open up the outer fuselage at the impact point. Hitting water at those speeds is like hitting concrete since water is not compressible.

The number and size of slides are dictated by airplane evacuation times not their secondary use as floatation devices and trust me, you want to keep it that way. Adding more exits & slides just to have more "rafts" would increase the cost and weight of the plane considerably and drive ticket prices even higher. Making the slides longer (to float more people) would have a negative impact on evacuation times and safety. Flights over larger bodies of water carry dedicated rafts based on their rated passenger capacity. In this situation I don't think it would have helped a lot and most passengers are already upset at the overhead compartment space dedicated to the flight crew and safety items. Adding in life rafts would just increase the frustration and operating costs of the airplane for no measurable improvement in safe outcomes over the continental US.

Adding any sort of a non-slip surface to the wing just for emergencies is not a good cost benefit trade. You are adding weight, drag (think increased operating and maintenance costs) and additional risk (icing, changes in stall behavior/margin) under normal operating conditions to offset a minor risk (slippery surface) during an emergency situation (loss of aircraft/major damage is a roughly 10E-9 type of event).

Can't help with the other ponderings.

- Eric