Beater, I disagree. I fly a SPIFR aircraft in an almost identical role to that of this pilot and it seems to me a timely, properly controlled IMC climb would almost certainly have saved this aircraft. A nightsun most probably wouldn't, after all the aircraft would already have had a landing light plus a movable searchlight.
[I have used nightsun quite extensively and taught its use (RAF SH (Puma), SAR and special ops (S-76 and Blackhawk) and UK police (AS355). As Jellycopter says, it's of limited use, counterproductive even, in very poor visibility caused by low cloud and fog due to glare and backscatter. Because night vision is instantly reduced, suddenly you can see nothing outside of the beam, at least until your eyes adjust. To attempt to get it fired up and pointing in the desired direction would have increased the pilot's workload further, at least for a short time].
As far as an IMC climb to MSA goes, minimum IMC speed and full power, wings level, ball in the middle. Increase speed to Vy once at a safe altitude. Or alternatively, a Class 1 helipad departure profile. Not sure why you asked that; it's fairly basic stuff, as per any night takeoff into IMC from a remote site.