Full-time indefinite traveler here. I haven't had a home address in almost 3 years. My biggest problem is finding a bag that will work for one-bag travel, but also will accommodate a day bag inside or on the outside of it.
Recently I've somewhat enjoyed using a non-Tom Bihn bag. (I KNOW!) It's the Osprey Ozone carry-on. It's a high-clearance 2-wheeled bag with a hidden backpack suspension system and a separate daybay that actually zips to the back. So it basically maxes out most airlines' 1 bag + 1 personal item allowance, but after you disembark the plane, you can combine the bags into one by zipping them together for backpack mode, or for wheeled mode you clip them together for better weight distribution.
There are a few problems I have it it. Osprey's material is that super-thin synthetic, so while that saves weight (which is then consumed by the wheels), I don't trust people I must still occasionally surrounder my bag to. Worse, since it has a really beefy suspension system and wheels, it feels like half the bag's capacity is used up by the bag. All told, I honestly believe its capacity is probably on par with the much smaller, much lighter Aeronaut 30 I have.
BUT... it has that killer feature. You have a day bag, that it combines with. The day bag doesn't go inside the main bag, but rather, attaches it to the outside. It's genius. It passes the airlines' allowances just fine, but lets me have both a real, fully functional day bag and a full-sized suitcase.
Tom Bihn needs something like that.
The closest Tom Bihn has is probably putting a Cadet or Pilot inside a Tristar, but then you're not left with much room for clothes. What would be ideal would be an EDC bag, capable of a 15" laptop, that zips to the outside of something like an Aeronaut 30 or 45. That way, when you walk to your accommodations, you only have one bag to carry, but when it's time to board the plane, you separate your bags and one becomes a carry-on while the other becomes a personal item.
(Honestly, bonus points if Tom Bihn made a waxed canvas option for the day bag. It's not as durable, but it's a lot more stylish around Europe.)