I am surprised with your experience that you would suggest Helos could fly and in brown/white outs...when it happens the top priority is getting out of it ASAP...not carrying out a hoisting land sequence.
Huge difference between picking up a wet, hypothermic father and his 8 year in Muskoka after they plunged through the ice and saving a downed F18 pilot under Taliban fire in Afghanistan. In the first case patient care is top priority, in the second security and speed (in and out)is top.
I understand where you are going with your idea of a V-22 application. Honestly I agree. I think domestic SAR should be passed on the the Coast Guard and a CSAR application stood up...it is the military after all. It's been talked about for years but it doesn't seem to be happening. If the CF SAR world does go the CSAR route then I might be inclined to agree with you. However, as it stands right now, the requirements of domestic SAR are not met with a V-22 based on its down wash alone.(IMO of course) I couldn't imagine trying to pick up the said 8yo above as he is blown about the ice by V-22 down wash.