
My take - the Selene.
Armed with 4 custom-tabled, heavy slashes that slowly slice target's hull to maximize area-on-effect. What she cannot destroy, she will leave crippled and in urgent need of maintenance. Diagonal configuration of side beams makes them capable of both firing forward and maximize firepower in front of the ship, as well as protecting broadsides of the ship.
She has armor of comparable rating to Orion, she has a sprint drive, she has advanced damage control systems, she has a hangarbay. She doesn't have superb point defenses and sublight drive. She doesn't need them when she's a fortress that can jump frequently. My doctrine of post-capella strike warships features subspace mobility as premier method of deployment and positioning, while typical defensive warships [like Deimos] have better sublight propulsion systems.
Selene is an Iceni-sized brawler designed to harass Shivan backlines and survive, when the regular fleet is doing defense. When she's done with one rally point, she can perform maintenence and reposition for the next attack without further assistance. Superior subspace mobility also makes her hard to counter with shockjumping. While she's a cruiser and corvette killer by design, pair of Selenes can effectively engage a Ravana.
This, along with next-generation cruisers answers the issue of Shivan midsized warships spreading around the inhabited terran and vasudan systems like a wildfire, but Selene isn't an answer for the problem of Juggernauts or securing subspace access to GTVA as a whole. I consider Selene as a small part of the answer and one of topics of broad debate about post-capella doctrine.