I found following Solutions for very similar combination (500/4 II, 5dm3, 7d, 24-70, 70-200, flash...):
1. Kiboko 22L+
http://www.cultofmac.com/184431/the...slr-backpacks-around-but-itll-cost-ya-review/
2. LensPacker 1
http://www.koenig-photobags.de/koecher-fuer-teleobjektive/lenspacker-1/
Combination 1 allows (I use it for travel by plain):
Left side: 500 (camera not attached) lenshood reversed
Right side: 2 boddies, 24-70/2.8 II, Flash
Many accessories and a 14" Notebook
Suitable for plain transport
Combination 2 ( I use it in the field because is completely waterproof):
500 with teleconverter and camera attached, lenshood reversed
Each of the 4 attacheble side expansion bags can cover a camera Body or any lens like 70-200/2.8 mrk II or smaller.
Suitable for airplain transport
I afraid the 22L+ is not produced anymore (replaced by Gura Gear Bataflae 26L, unfortunately no Laptop possible anymore)
The biggest negative issue of both solutions is the price.