Your comment about radar is typical - unless you have operated with our 330 degree radar and seen it's advantages (yes it would be nice to see ahead as well but clearing turns are simple and quick) and tried IMC letdowns to cliffs with awkward winds, you will not understand the argument.
Well, I have many hours in the Sea King and also using radars that aren't 360degs and don't have a blind arc. You are talking really only about a small proportion of the letdowns where a 360deg would be useful. It is so much easier to see your target or area all the time during a letdown. I can think of at least one occasion at night in the Sea King carrying out blind arc turns, and we still flew over a rock on the approach to the cliffs that the radar operator hadn't picked up in the blind arc clearance turn (and he was a very experienced operator). He saw it on the radar after we had passed it! Fortunately we saw it from the front in our landing lights and were able to avoid it, plus we were at 200ft and not lower. It wasn't foggy but it was very windy with lots of sea spray. Anyway, don't you use NVGs these days for letdowns at night so that you can see ahead?
Cyclic has really made the comment that I would have made. I would also say that the MCA S61s appear to do IMC letdowns to cliffs quite safely as will the S92. You just adapt your procedure accordingly.