It would seem fairly easy and affordable to develop a tie down system at least...
What, you think they're just stacking them up there, and letting them be?
Numerous systems are used to secure containers aboard ships, depending on factors such as the type of ship, the type of container, and the location of the container. Stowage inside the holds of fully cellular (FC) ships is simplest, typically using simple metal forms called container guides, locating cones, and anti-rack spacers to lock the containers together. Above-decks, without the extra support of the cell guides, more complicated equipment is used. Three types of systems are currently in wide use: lashing systems, locking systems, and buttress systems. Lashing systems secure containers to the ship using devices made from wire rope, rigid rods, or chains and devices to tension the lashings, such as turnbuckles. The effectiveness of lashings is increased by securing containers to each other, either by simple metal forms (such as stacking cones) or more complicated devices such as twist-lock stackers. A typical twist-lock is inserted into the casting hole of one container and rotated to hold it in place, then another container is lowered on top of it. The two containers are locked together by twisting the device's handle. A typical twist-lock is constructed of forged steel and ductile iron and has a shear strength of 48 metric tons.
The buttress system, used on some large container ships, uses a system of large towers attached to the ship at both ends of each cargo hold. As the ship is loaded, a rigid, removable stacking frame is added, structurally securing each tier of containers together.