The problem with this idea
If you have beds where the cargo should be then you have no space to put the cargo. That might mean bags but also any other freight that passenger aircraft routine carry when they have capacity.
Maybe the solution is to knock everyone out before they board and revive them on the other side. Then there is no need for toilets, food, entertainment, overhead luggage compartments, bins, or most of the flight crew. Stack them up on pallets 3 high and load/unload them up on a forklift. (joke)