I have played around with the ship disign thingy and have created this one.
Note: This is no actual ship design, I only used this to try a few things.
New Class class Cruiser 32700 tons 2211 Crew 5120.2 BP TCS 654 TH 810 EM 1800
1651 km/s Armour 15-91 Shields 60-300 Sensors 64/64/0/0 Damage Control Rating 31 PPV 72
Annual Failure Rate: 275% IFR: 3.8% Maintenance Capacity 3034 MSP Max Repair 320 MSP
Magazine 2620
MTU Typ 60/75 Ionentriebwerk (18) Power 60 Fuel Use 70% Signature 45 Armour 0 Exp 5%
Fuel Capacity 350,000 Litres Range 27.5 billion km (192 days at full power)
Grundig Gamma/2 Schutzschild (30) Total Fuel Cost 420 Litres per day
Krupp AMS-70 (2x4) Range 1000 km TS: 16000 km/s ROF 5 Base 50% To Hit
Rheinmetall Wespennest(S) ASR Werfer (12) Missile Size 6 Rate of Fire 60
Siemens Typ 1,9 ARR Leitsystem (1) Range 1.9m km Resolution 1
Siemens Typ 144 ASR Leitsystem (1) Range 144.0m km Resolution 50
Rheinmetall Falke II ASR (437) Speed: 18,600 km/s End: 59.6m Range: 66.6m km WH: 7 Size: 6 TH: 86 / 52 / 26
Bosch Typ 2,4/0 Radarsystem (1) GPS 240 Range 2.4m km Resolution 1
Bosch Typ 288/90 Radarsystem (1) GPS 28800 Range 288.0m km Resolution 90
Bosch Typ 25,6/20 Radarsystem (1) GPS 2560 Range 25.6m km Resolution 20
Telefunken Typ 64 Wärmesensor (1) Sensitivity 64 Detect Sig Strength 1000: 64m km
Siemens Typ 64 EM Sensor (1) Sensitivity 64 Detect Sig Strength 1000: 64m km
I used the largest passive and active sensors I have currently designed, but I realize, those are way smaller than yours, so I have a mass-advantage there (not an intel one though). I would, however, use a dedicated fleet scout, that will hang back a couple million km if the need for longer range sensors comes up.
The big thing I did was using unarmored engines. If your armored ones mass 450t (I have never tried armored engines), as you said for your moster battleship, by this I save 3.600t. This alone would allow to up the armor to 9, which, IMO, is much better protection than armoring the engines alone.
Just to see what can be done, I used the saved mass from my smaller sensors to up the armor and shields even more, giving me a real "Ironclad".
I also use engines, which do not trade power for fuel efficiency/safety from explosion on the theory that by armoring up my ship and being faster, the engines will be less likely to be hit (by the time the armor is breached, the ship will be out of ammo anyway and being slow as it is, it _will_ go down enventually)
I realy like the massive magazines, your ships have
Your ship is also very, very fuel efficient. I would have to at least double the fuel storage in my ship to make it viable. But while fuel efficiency will bring you to the battle, it won´t help you _in_ the battle, so I practically never trade speed for range (in military ships, that is).