Here are a few hull types I've cooked up based on some BFG models I converted. The Phalanx is a Avenger class Grand Cruiser with the Prow of a Despoiler class. The Phaeton has one of the engine pods from a battleship, and the Confessor class is has a Stylx class bridge and is covered in spires.

Phalanx Class Grand Cruiser
Dimsensions: 7.2km length, 1.4km abeam
Mass: 40 megatonnes
Crew: 130,000
Accel: 2.2 gravities max sustainable acceleration

A fleet support vessel used in the Mercasian Crusade of M36 to conquer what would become the Selveria Sector. Ships of this class played a vital part in a number of pitched battles where they protected high-profile vessels from torpedo and boarding craft.
The Phalanx class is huge lumbering craft borrowing many of it design elements from the Avenger and Despoiler classes of Grand Cruiser. The majority of the surface of the ship is given over to rank upon rank of defense turrets ready to fill the space around it with an all consuming cloud of exploding shells, las bursts and other stranger things.

Speed: 4
Manoeuverability: +5
Detection: +10
Hull Integrity: 90
Armour: 20
Turret Rating: 4
Space: 90
SP: 70
Weapons: Port 3, Starboard 3

Grand Cruiser: This ship can use Cruiser Only components.
Fleet Defender: Using it's huge number of turrets to saturate an area of space the Phalanx Class can lend it's turret rating to a friendly vessel withing 3VU. As an Extended Action an Explorer makes a Difficult (-10) BS test, for every degree of success the friendly vessels turret rating is increased by 1 to a maximum of +4.

Phaeton Class Battlecruiser
Dimsensions: 5.2km length, .8km abeam
Mass: 31megatonnes
Crew: 98,000
Accel: 2.4gravities max sustainable acceleration

Developed by the magi of the Forge World of Terzan Prime early in the fifth century of M39 as a response to the escalating predations of a race of advanced abhumans known as the Valkyrin as they raided deeper into the Selveria Sector. The Frigates and Destroyers of Battlefleet Selveria could not bring the necessary firepower to turn back the invaders, and by the time capitol ships could be brought to bear, the nimble and quick Valkyrin ships were already on their way back out of the afflicted systems.
The Phaeton class Cruiser was fitted with an abnormally large drive system, typically reserved for Battleships. This would allow it to keep pace with it's smaller escort craft as they ventured out system to meet the Valkyrin head on. Unfortunately, by the time the first squadrons of Phaetons were constructed the Valkyrin raids had precipitously dropped in frequency.

Speed: 7
Manoeuverability: +10
Detection: +10
Hull Integrity: 70
Armour: 20 (24 prow)
Turret Rating: 2
Space: 69
SP: 68
Weapons:1 Prow, 2 Port, 2 Starboard, 1 Dorsal

Battlecruiser: This ship can use Cruiser Only components.
Navy Warship: The Phaeton Class Battlecruiser comes pre-equipped with the Armored Prow component. This component cannot be removed and has already been factored into the vessels available Space.
Running Hot: The oversized engines of the Phaeton class place considerable strain on any plasma drive used to power the craft. This severe power drain of can cause dangerous fluctuations in the midst of battle. Every time this vessel suffers a Critical Hit, there is a 25% chance of a component (selected by the attacker, from components they know about) losing power.

Confessor Class Cruiser
Dimsensions: 5km length, .8km abeam
Mass: 29megatonnes
Crew: 85,000 crew,
Accel: 2.5gravities max sustainable acceleration

A long range patrol and picket ship, the Confessor class Cruiser is the eyes and ears of Battlefleet Selveria, operating out in the far fringes of the Sector and even into the depths of the Sandillion Gloom. Based upon the Lunar class hull, the Confessor is bristling with the tall and spindly augury spires, running up and down its entire length.

Speed: 5
Manoeuverability: +8
Detection: +20
Hull Integrity: 70
Armour: 19
Turret Rating: 2
Space: 75
SP: 61
Weapons: 1 Prow, 2 Port, 2 Starboard

Overall, I like the hull-types. My feedback:

The Fleet Defender trait on the Phalanx would be more appropriate to a Frigate or Cruiser in a dedicated escort role. Rather then lending their full turret rating, the escort with the Fleet Defender trait could grant a +1 to the Turret Rating of an ally within 3 AUs. That way Frigates and Cruisers have a believable and realistic role within a battle, and a small swarm of escorts could radically increase the survivability of an ally against torps and boarders for as long as they are alive.

The Confessor should have a minor trait to balance out its enhanced detection, similar to how you've balanced the Phaeton's speed with its Running Hot trait. Perhaps play up the fragility of the extensive sensor vanes. Perhaps every hit that penetrates the Void Shields has a chance to damage the auger array as well? Perhaps a 1 in 10 chance or whatever is appropriate.

In any event, nice ideas! I'll be stealing the Fleet Defender idea for sure.