So, we need something to act as a missile platform, that can avoid their ASM, that is hard to detect.
You are thinking sub, and that is fair. Bomber, somewhat fair too.
But you are missing another technology, with bigger payloads than bombers, harder to shoot down and more amenable to our tech base than sub: The ground effect airplane.
UF-GEV-45 "Ekaterina"What if we made a plane which doesn't fly? as heretical as that sounds, it can actually be a good idea.
It is a well known fact that when flying very close to the ground, lift is vastly increased due to the ground effect. Most planes only fly through there briefly, but one specifically designed to fly in that altitude range with wings made to fully exploit that effect can achieve significantly greater performances... at the cost of never being able to actually fly. Using it on unever ground would be extremely risky, which is why we instead use it as a ship.
Ekaterina is a large plane with short stubby wings, made to fully exploit the ground effect to generate lift, with a high aft-placed horizontal tail to maintain stability. On top of the wings (near the hull) and on the tail there are 4 powerful turbofan engines powering it.
The top of the plane is flat, allowing it to house its weapon systems. Thanks to the ground effect , it is designed with a goal of 4 missile clamps for saltseeker missiles, plus a dorsal (unarmoured) turret housing a sewing machine and a pair of SAM missiles. Clearly it carries countermeasures and radar as appropriate for a plane, but mounted to be released on top rather than on the bottom. It also has a radar appropriate for its size. Its top is painted with UV reflecting paint.
Being unable to take off and limited to water use, it can in many ways be considered a ship. it uses a boat hull which allows it to take off and land from water, and it can be resupplied by carriers, meaning that even if we need to sacrifice a bit of range for the sake of payload it will still be able to follow and support the fleet.
The goal is a relatively small (compared to the large ships currently launching the saltseeker), fast ( very fast compared to any ship), low flying, high payload (compared to a plane) vehicle, able to sneak past enemy radars to deliver its deadly payload, then quickly come back. With its speed and size, it should be able to avoid the enemy ASM, while the turret provides protection against AAM, with the added bonus of the ocean below turning near misses into harmless duds.
UFAF-SNB-45 'Tubby Duckling' (1) : Madman
Microprocessors (1) : RAM
Ekaterina (1) : Andrea