Don't get all excited about wearing a 100lb ruck for BMQ. :camo:
It's been a while since I was involved with a BMQ course, but I BELIEVE you do a single weekend in the field, probably in Feb/Mar so it may or may not even be in the snow depending on the weather in Aldershot. Even if it is, we use winter warfare tents so while you will carry a ruck, most of your section kit will be in a toboggan that you will all be hooked to like sled dogs.
If I had to guess, my ruck is max somewhere around 60lbs (probably less) for a field weekend.
Trust me, carrying more kit than necessary will get old fast. Focus on getting the paperwork completed properly as quickly as possible and jumping through all the hoops necessary to get sworn in first.
Good luck.