So if something happens, you're just going to throw whatever is at hand into a pack, and set off for the "great wild" to rough it out, high-tech caveman style? That is an amazing BAD unplan, no offense. While I don't always agree with everything Duncan Long says, or how he says it, he sums up the problems with that theory pretty well.

You look at the Norrona and you see a really big backpack; I look at it and see a lot of high quality thread making thousands of stitches. If you load this thing with things that don't float, you will overload those stitches. I also see a lot of fabric that can be cut, poked and abraded through with very little difficulty, if you are tossing things in there willy-nilly, you'll kill it. And possibly tear a hole in your back before you are done.

Assuming you can actually move with this much weight on yoru back. What percent of your body weight is 40kg/88lbs? Anything over half your weight is just BAD if you have to carry it for any length of time, and I would recommend no more than a quarter-to-a third your weight if you are in shape.

I think for what you have in mind, your best bet is to completely avoid an internal frame pack. An external frame pack with a cargo shelf is very forgiving of bulky and badly packed items, and they are more comfortable IMHO for heavy loads. I've even seen them with Pelican cases bolted to them and it didn't feel as uncomfortable as it looked, even if it was unwieldy.

But not matter what you go with, your best bet is to have your core in a pack, and most of it in your vehicle or a cart.

But the question of what are you putting in this pack still stands as a key one, and just as key, do you have a destination where you are expected if you have to bug out?