My Jane's email updates reports that we are doing this:
The US Navy plans to send an amphibious ship to the Gulf of Guinea as a 'floating school house' for regional navies as a pathfinder effort to establish a lasting maritime presence off the western coast of Africa. The deployment - which will run from the third quarter of 2007 until mid-2008 - overlaps with the creation of US African Command (AFRICOM)[.]
This doesn't offer anywhere near the capabilities of a formal MOB, but it is a start.
UPDATE: A timely press conference on AFRICOM included this answer:
AFRICOM is not designed to result in any new troops on the continent, and it's not designed to result in any new basing structure. Rather, it is a way to organize our efforts.
This approach doesn't address the fact that bases really are needed to project power. But if not on the continent, off of the continent will work. Especially since local militaries (should any be hostile) don't have the same capabilities for hitting ships at sea as is found in other areas. Mobile offshore bases could be just the ticket for nearby bases to project forces for humanitarian or other purposes. One purpose would be to host rapid reaction forces nearby to help protect AFRICOM headquarters located in African countries. And such bases maintain a forward presence for military-to-military contacts.
We might very well use a number of these types of bases from West Africa, south around the Cape, and north to the Horn region. Being mobile would help react to developing crises, too.
