Mark, you are not the only bloke looking for the perfect bag, you should see my collection! Now in my late 60s and still working and travelling (long-haul like you), I need space and comfort as my ageing frame comes under pressure. I have a 12.5" Lenovo Thinkpad Yoga and a Galaxy Note 8, however I have still opted to order the 15" bag to carry files, papers, medication, Trent Cruiser power unit, spares, spare clothing ("A fool and his underpants are soon parted") etc. My philosophy is: if my check-in luggage goes astray, I can still start my work assignment.
Question: what is the inside length of the side pockets that can be used for water bottles etc? I ask because I like to keep stuff together in smaller pouches/containers eg I use an old stationery pouch for my power adapter & cable, adapter plug if not UK etc).
Regards, The Jolly Roger