It's not so much the virtues of rescuing by landing as opposed to hovering, as the extreme long range/high capacity you get from a flying boat. I've often thought that it'd be a good capability for the Navy/CG/ANG to have out in the Pac for long-range SAR. Put a few in Kodiak, Guam, and K-Bay, for example. The Japanese are still building and flying this big bastard, and apparently the Indians are looking at buying them too:
An AAR-equipped helo or V-22 would probably make more sense.
Ahh, the US-2...
All that said I think it would just be a nice to have, the US-1/2s can land in pretty rough seas for a seaplane due to it's unique hull .