You haven't mentioned the nature of your trips with the one bag system. In general, nothing can beat the weight of a single pouch (your current proposal), but the problem is it is hard to use this system if you need to have a jacket and tie meeting right after landing. I am a wheeled one-bagger (I don't like carrying anything on my shoulder) and I find the Gate8 bag to be good for my needs. Its dimension checker url is here. I travel Lufthansa frequently and have never been stopped for a weight check (I travel with 5 days worth of clothes), but that may be because I've not travelled economy much on Lufthansa, but given changing company policies, I will be soon, and may encounter these checks. I find the Gate8 bag to be very light as well, but its wheeled - so it won't be as light as your current system.