Product idea: ISO-standardized luggage cassettes. Like ISO shipping containers, but luggage sized. Such cassettes would make it easier for airlines (and other transport companies) to load and unload planes robotically, and each passenger would be guaranteed a defined amount of space. The luggage cassettes would be designed such that you can combine them into various configurations (2 x 2, 2 x 4, 4 x 4, etc), if you needed more space.