You may soon be doing so, and willing to pay for the privilege. From Wired
Airlines buying certain planes from Airbus will soon be able to order new “passenger modules,” the exact size and shape of a cargo container. They can slot them into the belly of large planes, just like they load your luggage, in a large metal bin. They can also pull them out again for shorter flights or when they need more cargo space.
If the concept works, and airlines find ways to use the bunks to make money without robbing too much cargo space, bunks could be just the beginning. Airbus also showed plans for a lounge, a conference room, a medical suite, and a kids play zone, all to be slotted into the cargo hold. One day, the entire plane could feature swappable modules instead of permanent, regular seats.