The Searay class was born out of wartime need. Starfleet needed a fast scout to act as they eyes and ears of its advance battle fleets, as such a ship that was faster than the Heston and Constitution classes was required.
The Searay added a pair of nacelles to the basic Hermes class scout design, the resulting ship was immensely fast for short periods, but notoriously short ranged. Given the mission profile intended for the class, this trade off was deemed acceptable.
The 12 ships built performed well, but were not retained postwar in operational service as the short range handicapped their performance in most peacetime roles
The Marauder was an even more extreme reaction to the lessons of the Four Years War, initially planned as the second ship of the Mary & John class, she was modified during construction to mount three warp nacelles.
Proposed as a Dreadnought Destroyer, the realities of the peace time Starfleet should have condemned this class to history as a mere single ship footnote, however testing revealed the warp speed capabilities of this class. Starfleet put the class into limited production and in total six ships were built, and were utilised as rapid reaction craft on the sparsely patrolled Tholian border for many years.
The Mary & John class Battle Destroyer was designed as a destroyer counterpart to the Heston class Battle cruiser and Federation class Dreadnought, utilising the same saucer design as those classes, with the upper nacelle mount from the Federation. Owing to wartime prioritising of existing designs, the USS Mary & John finally began trials in November 2257.
In common with the Twin Saladin and the Warhawk designs, the twin engine configuration was a reaction to the lessons of the four years war.
This class, however, fell victim to another lesson from the war Starfleet realised that a rationalisation of destroyer designs was required. Only the Warhawk class entered service, the USS Mary and John saw only limited service as the Heston/Federation class primary hull lacked the science facilities of the Constitution derived saucer of the Warhawk class, and as such was ill suited to the peacetime Starfleet.
The Copperhead was a one off command cruiser, created from a Class I primary hull, coupled to a specially converted shipping container coupled to warp drives.
The design was conceived to meet an urgent need for a command ship capable of controlling operations across a broad battlefield. The single Copperhead, with a strategic operations crew of almost 400 could easily coordinate hundreds of ships across the entire battle space.
The end of the war in 2256 meant the Copperhead was left with a mission, as the peacetime Starfleet could ill afford the level of resources required. The sensor and communications equipment was still of use, so the ship was redeployed to fill a role providing intelligence around the Romulan Neutral zone.
The Mindbender class was an experiment using the same components as the conventional Federation Class Dreadnought, but creating a more compact craft to reduce target cross section. Just one prototype was built and was used in competitive trials against the Federation class. The Mindbender was more manoeuvrable. but top speed suffered as the design was less warp dynamic, it also suffered from restricted firing arcs for the primary hull lower phasers.
After the trials were complete Mindbender was retained as a trials and training ship.