Thought I wanted to share this with you since I'm quite excited about my new bag!
The ideal photobag doesn't exist. Some of us have been searching for years and have a wardrobe full of bags to prove the point!
But the Tenba Shootout Daypack comes close to the ideal IMHO. I bought it for our trip to Greenland and I really like it. It easily held my substantial loadout (two bodies, FA*28-70/2.8, D FA 100/2.8 macro, F 70-210/4-5.6, FA*300/4.5, DA10-17, DA12-24 (all lenses with their hoods), tele converter, polarizers, batteries) while remaining well within the carry-on regulations of even the most stringent airline.
When you're off the airplane you can expand the bag so as to hold a jacket, sweater, gloves, etc!
It doesn't hold a laptop, that's perhaps a downside to some.
It is not cheap but it is extremely well made and should last a life time!