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FIRST THINGS FIRST ...

Most answers below SEEM to make a very strange assumption - that today's designs are up to future threats.

This MAY be true for mid-ocean warfare, but for future coastal/littoral warfare there are going to be many, many more drones, which with increasing technology and AI will be self-commanded and not susceptible to ECM.

The vessel MUST be armed with weapons with the capability to handle numerous under-, on or above the sea drones ranging in size from small and numerous to large and fewer.

The larger ones MAY be worth using a very expensive missile on, but the smaller massed drone attacks are still problematic. They can, with sophisticated programming and AI, be targeted at electronic sensors or weapons so whilst they may not be able to destroy the ship(s) they may mission kill them.

So the first thing is to design the "drone killer" weapon(s) or at least specify the space and services needed to install them aboard.

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