Glad to see your idea worked! I've thought of getting a MH Scrambler as a summit pack for multi-day snowshoeing trips, but was worried about the problem with the pad that was, according to some reviews, difficult to remove (like you said).
I settled on a Black Diamond Bullet, which weighs in at 13.9 ounces, that is very supple and easy to pack. I tried to do it like you did (put the small packed pack in the other pack), but for some reason, it didn't seem "right". I should try it again sometime.

Like you, my SAR pack is my dayhike pack. Either an Osprey Stratos 32 (spring, summer and fall) or an Osprey Switch 36 (winter). I bring the same basic stuff for both activies, but add some stuff for SAR : a heftier first-aid kit, 60' of 10 millimiter rope, a full-featured compass, GPS, all-weather notepad, Ironclad heavy utility gloves, a small sleeping pad, 3W Luxeon flashlight... off the top of my head, that's about it.