I have a different perspective on LCS to most and while not overly impressed with it's execution I am in favour of the concept.
The US Navy is massive and more able to absorb the overheads of single role ships / platforms than pretty much any other navy, throw in the fact they are supported in certain mission sets by organisations that conduct duties other nations usually assign to their navies, that is the Coast Guard especially but also Customs, even the US Army logistics / landing craft / ship capability and other organisations, they have less need to concern themselves with the low end of the equation.
However the USN still needs to cover off mine warfare, inshore / littoral patrol / SF support / ASW / anti surface, in an expeditionary setting. These missions are currently conducted by a range of specialised ships and craft that are not really suited for anything but their designed role. These craft could be replaced by uuv/usv/uav based capabilities added to major combatants or deployed by large amphibious vessels, but due to their size, expense and versatility will never be available in the required numbers and would likely be deployed on higher priority tasks.
To increase the numbers of destroyers and amphibs, even just to add flexible capability to the existing fleet, the USN needs more funding or to reduce costs. Steel is cheap and air is free meaning most of the acquisition costs are related to the systems on the ships, not the platform it's self, i.e. a smaller less capable destroyer, LPD, or new generation frigate, will either not be that much smaller, or cheaper, unless it is significantly less capable and flexible. End result, you are paying 70-80% the acquisition and operating cost of your big ships, for less capability in key roles and far less flexibility for supplementary roles because the shop is smaller. This means you have fewer destroyers and high end amphibs, a class of less effective, single role frigates that can't do anything the destroyers can't and are less effective and capable in the shared roles than the destroyers are, and you still need your single role MCMVs, PBs etc.
This is where the LCS concept comes in. It is baseline patrol vessel with corvette / patrol frigate level offensive and defensive capabilities that can affordably replace the single role vessels, without cutting into destroyer numbers the way a traditional guided missile frigate would. The mission modules, or more to the point, their capabilities are set, those capabilities are needed whatever ends up carrying them, the issue is do you cut into destroyer numbers building three frigate instead of two destroyers, or worse five frigates instead of four destroyers and still need the small vessels with no combat power of presence at all, or do you replace the single role craft and old frigates with a ship that cost one third what a destroyer does and leave the destroyer numbers alone?
