A cube would maximise the volume while complying with the 62-inch limit
Maybe true from a mathematical point of view, but in reality cube suitcases would be:
- Harder to carry with a handle, you will have to stretch your arm away from your body, which will make things feel heavier.
- It will be harder to walk while carrying them.
- What about long objects you can easily put inside the normal suitcases?
It will also be much less likely to fall over
True, if it was the only suitcase. False in reality because it will be harder to place cube suitcases in containers on top of each other, this will make them much more prone to fall causing damage to them or to luggage handlers.
A disadvantage will be a great depth, with things packed many layers deep, so you'll have to unpack before you can access things in the lower layers
This is true for one person, a person will have one or two suitcases, but a customs agent will have a hell of a job because scanners will not be that effective due to the many layers, and manual inspection will be difficult. That's the reason why you have to put your luggage flat when you scan them, to make the scanner more effective. Making luggage condensed by default will be a big problem from security point of view.
When placed on a table or a bed in a cramped hotel room, it will take up less space on the table or bed.
I disagree, whatever space you save on one axis, you will get it in the other axis. Having a normal suitcase along the wall is indeed more space friendly than having a cube shaped suitcase with less space on the wall and much more space away from the wall.