I think "The Travel Line" by Peak Design might be the best example of a true "One Bag Travel" for non-business related travel. If you have to wear a suit, I am not sure how well this would work for business travel. Peak Design puts out top quality products. They really put a lot of thoughts into their products. Having your hands free and one bag on your back seems life changing...if you travel a lot.

With regards to the total weight have the bag, I think the difference between a bag 30L to 45L range, the 1 to 2 lbs difference is not really that big. Here is The Travel Line compared to some of the other "top bags" on the market.