Wow, what you need bigwig, are pack goats. I'm only half kidding. I've had the same issues, but to a lesser degree. I have two large backpacks that do the job. Like others have said, you can't go wrong with one of the huge Dana Design packs. I have the external framed version of the Terraplane, called the Terraframe. It's basically the same pack (almost) coupled with the external frame. It's a real load hauler but terrible when off-trail.

My other one is a McHale expedition pack. It's so old I think it precedes his Inex, but it equals or surpasses the Dana in how much it can carry. Mine is used, and since they are custom made packs it's very difficult finding a McHale that fits well, unless you have one made for you. And they're pretty expensive.
But with the loads you are talking about it might be a solution for you. I feel they are the best heavy duty packs available.

Cliff