I've wondered about how modular surface weaponry could be adapted to use in the sea. In the spirit of the old Q-Ships, seems like parking a few Paladin self propelled artillery pieces on the deck of a container ship could provide a cheap bombardment platform, for instance. Put a patriot battery on same and you have air defense, add a squadron of Av-8Bs or F-35 STOLs and you have an inexpensive platform for launching long range sorties, and the whole thing can be whipped together in a few weeks in an emergency.
I can't imagine a situation where the existing naval assets wouldn't be enough, but I bet there are contingency plans to that effect in some dusty file cabinet.