Interesting though discussion about potential AFCS performance to enable approaches to below Cat 1 ILS limits is, it is surely not particularly relevant to this accident's cause. Just 3 mins after the accident time, the wx at Sumburgh was not that bad - 2800m vis, scattered 200 and broken 300ft. The acft crashed 1.5miles away - almost certainly where wx was similar. Getting visual safely should not have been hard. We still come back to the progressively reducing airspeed and height below profile. There is no logic to a deliberate action of chosing this profile, surely? Why try and descend early when the airfield is pretty much at sea level anyway, and that's where you've been told the wx is ok?
Incidentally, would the approach just have been monitored horizontally on the localiser/DME, or would the crew have been monitoring an AD GPS waypoint too as back up?