This is an option, though not cheap.
I found it while researching convertible carry on luggage, which means it has backpack straps vs. wheels.
What is nice is that they open up like traditional luggage, clam shell, and have specific compartments for tablets, laptops, etc.
Opening up fully like a clam shell makes them easier to get through airport searches and to quickly accessing items at a hotel, hostel, etc.
http://www.tortugabackpacks.com/
I am looking at the Tortuga Air, which would definitely require applying UL techniques from backpacking to urban travel….27L or 1662 cu in.
The Tortuga Backpacking is pretty cool, but seems large for UL/Lightweight travelers at 44L or 2685 cu in.
Here is one that I just bought on sale for $55…$69, but $15 savings on 1st order if you sign up for their mail list.
http://www.ebags.com/product/ebags/tls-mother-lode-weekender-convertible-junior/241465?productid=10209116
ebags….more of a carry on luggage that has backpack straps.
2538 cu in.
Better than most like this with a solid reputation, but the sucky waist belt makes me think that carrying this as a backpacking would only be for short distances where the Tortuga looks like something you could carry all day.
I picked up for when I am traveling with my daughter for her gymnastics competitions, so traveling light is relative or limited….but for the two of us, should be fine.
Probably overkill for one person going UL.
Right tools for the right job?
P.S. Big Thank you to Ben 2 World for all of his great advice on this subject. He is a wealth of knowledge.
Tony