I think you underestimate the difficulties here. Maintaining an exact height in the high hover in open ground is spectacularly difficult. The SAR boys, who practice that sort of manoeuvre all the time (as a means to avoid re-inflating a collapsed parachute canopy), keep the winchman at constant height above ground by continuous small adjustments on the hoist. Trying to do it just by voice marshalling to the pilot is virtually certain to result in the winchman touching down at some unintended point at some stage in the process.
Sven, I can't argue with you that it might be difficult to hover at fixed altitude at fixed position as I am not RW. But I have spent some time dangling under or abseiling out of helicopters and I have certainly seen it done. We used to abseil out of Pumas from about 100ft (see pic) and I know the helo hardly budged at all as in training we used to take turns to be the safety man on the ground at the end of each rope, ready to heave if one of the abseilers lost control.
Also, I don't think that you could effect a rescue of a badly injured casualty, with significant bloodloss, unless he was horizontal in a stretcher. That would mean that the rescuer would have to touch down alongside him anyway, so wouldn't the precision of a winch would be redundant once the rescuer was on the ground alongside?
I don't deny it would be difficult and dangerous, doing it without a winch, but surely it is not impossible?
