The idea of putting military equipment in containers and placing them on military ships is not new, neither is the idea of quickly converting civilian vessels to military use, nor of modular barges. The USS Independence (LCS-2) and competing prototype littoral combat ship both have modularised mission modules, as does the HDMS Absalon.
There are obvious problems in using a module which is much larger and heavier than usual military containers. There are also problems with taking a civilian ship and using it for military purposes. To reduce the risk, DARPA are looking to use the containers first for disaster aid missions, not combat.
An obvious alternative to using a civilian ship is to use a military cargo ship. One option is the Joint High Speed Vessel (JHSV), which the US military are buying ten of. This is a high speed vehicular ferry with minor modifications for military transport. It has the advantage of having a large covered deck for holding containers. Such ships might be used most of the time for civilian cargo and only pressed into service for military use when needed.
One option which the DARPA report needs to consider is lowering the specifications of standard ISO shipping containers. These are designed to be strong enough to be stacked six high when full of cargo. This requires a very heavy, usually steel, construction. It is unlikely that military containers will ever be stacked more than two high and will usually be very light, due to having empty space for personnel and equipment access. As a result they could be built much lighter. Such containers could then be transported by air and handed by much smaller ground equipment and used on smaller ships. This is something I suggested for the use by US Air Force for "Prepositioning Strategies for Air Force War Reserve Materiel".
The Tactically Expandable Maritime Platform (TEMP) program will investigate and develop modular technologies and macroscopic modular systems that leverage ubiquitous International Organization for Standardization (ISO) containers and the intermodal transport system to deliver flexible operational capability from unmodified commercial containerships. The program has three primary objectives.
The first objective, corresponding to Technical Area One, is to broadly explore the concept of forming macroscopic integrated systems out of twenty-foot containers, identifying innovative architectures, mission applications, approaches, and enabling technologies.
The second objective, corresponding to Technical Area Two, is to conduct focused architecture development and preliminary design work on a TEMP humanitarian assistance and disaster relief (HA/DR) package. This package design will encompass modular technologies with the range of capabilities necessary to complete the HA/DR mission, such as situational awareness, command and control, and distributed micro-logistics over broad coastal areas without dependence on local infrastructure. The third TEMP objective, corresponding to Technical Area Three, is to demonstrate the viability of ocean deployed modular technologies and systems operating independently from a host containership. The program will design, build, demonstrate, and transition an exemplary system, the Modular Sea Depot - a multi-unit maritime logistics node. The Modular Sea Depot provides near term operational capability, while serving as proof of principle and risk reduction for a larger scale Modular Seabase concept.
From: "Tactical Expandable Maritime Platform" (TEMP), Solicitation Number: DARPA-BAA-10-57, Defence Advanced Research Projects Agency, April 2010