First of all, let me clear up a misconception that several posters seem to have: The Marines have *already* set up an elite unite opconned to SOCOM.
http://tinyurl.com/3yghq9
That is, it is not up for debate. The point cannot be argued that they shouldn't do it, because they have already done it. Savvy, all?
The second point was that "Marines" are unique in international law as being permitted to guard embassies, unlike soldiers, who are forbidden to do so. Therefore, if you want a uniformed guard, they at least have to be *called* "Marines", even if they work for Blackwater security. They don't have to wear Marine Corps uniforms or have ever served in the Marine Corps, yet they have to be called "Marines".
Finally, as to organization. Donald Rumsfeld reorganized the US Army from its traditional divisional organization to that of organic brigades. He did this based on the estimated best organization of the Army for future wars.
The Marines, though they would most likely have a far different organization, also need to be reorganized into units that give them optimal command and control and combat efficiency in the future. The best minds in the Corps Command and General Staff will be the ones who have to figure out what, exactly, this new organization will be, based on what they project are the future conflicts the Marines will have to fight.
The one thing that is certain is that the Marine Corps current unit configuration will not continue. It is just not optimal for the fighting the Marines will have to do in the future, and more than using spears instead of rifles.