It also is simply not true that tech crew cannot provide navigational guidance to pilots; that is exactly what happened pre-NVG at night at low level using the FLIR. Unhelpful, provocative and outdated.
Louis, the key word you used is guidance, they do not control the letdown in the same way as a military radop would and the responsibility for terrain clearance remains with the pilots whereas that role was held by the Radop.
I have plenty of friends and ex-colleagues in the new SAR service so I am not talking from a position of complete ignorance - I have flown the 139 in the SAR fit and had to approve certain letdown profiles being taught to other nation's students. The rear crew could observe, monitor and assist but the responsibility remained with the co-pilot.
As I said earlier, I suspect that some SAR rearcrew play a much more 'traditional' role in any radar letdowns.