The best defense is a good offense, or.....
Preparation in advance.
A few thoughts:
1. Pipe railing: Like what has been mentioned, staying on-board is the best solution to a MOB situation. To this end, on bigger boats, what I'd like to see is a replacement for "life lines." A one-inch stainless pipe railing.
Some of the older Taiwan-built boats had pipe railings but most sailboats just use plain old plastic-coated "life-line" cable. There are several problems with the cable such as flexibility and strength in the system, to name two. I would feel much more confident with a solid pipe railing.
2. Better hand-holds or swim step: Another area that could stand improvement is in the stern ladder boarding area. For example, our boat has the walk-though transom with a drop-down boarding ladder. However, the transom is sloped so that it could be difficult to make the transition between the ladder when it is in the down-and-deployed position and being inside the walk-though portion. What is needed are some handholds for the in-between area, or perhaps better yet, and in addition, a drop-down or fold-down "swim step" (as they call it on powerboats).
3. Lifting system: Lifting a wet and water-logged person on board over the toe rail is difficult at best. One problem is a person can slip out of some harnesses. What is needed is something more like a climbing harness which is more difficult to slip out of and which keeps the lower part of the body down low if it is connected to a lifting device. I carry a bosuns chair along which could be useful for a person without injury problems and who can get into it.
Preventer: Another thing helpful is a block and tackle with quick releases, such as used for a preventer. This connected to a climbing harness and tailed to a winch could lift quite a load. I use a large Shaffer preventer connected to the main halyard to ship a 115 lb Avon dingy with ease. The downside it that it takes time to set up and deploy. It's one thing to do use this in a calm anchorage but another to do it under adverse conditions. However, it's just another item in the "bag of tools".
Having surfed while holding on a line being towed by a sailing boat, even at only a few knots, I can attest to the fact that a person in the water holding onto a line of a moving boat receives huge forces. This could be really damaging to hands and arms if the boat is moving any more than even walking speed.
You folks in warm-water areas are fortunate. The Northwest water is so cold that you get cold-water shock right away and it's all downhill from there. Hypothermic conditions start setting in after a matter of several minutes.