First, I want to say that there doesn´t seem to be something inherently wrong with your designs, and they will do the job you want them to do, I just don´t think they are a very _efficient_ way of doing that job.
Your Chatham are incredible fuel-hogs
I modified a Battlecruiser of mine to carry what your Chatham has:
Leander - Copy class Battlecruiser 26,000 tons 281 Crew 1914.1 BP TCS 520 TH 1596 EM 0
3069 km/s Armour 1-78 Shields 0-0 Sensors 1/1/0/0 Damage Control Rating 6 PPV 0
Maint Life 0.56 Years MSP 299 AFR 832% IFR 11.6% 1YR 536 5YR 8033 Max Repair 108.3 MSP
Intended Deployment Time: 6 months Flight Crew Berths 2
Hangar Deck Capacity 5000 tons Troop Capacity: 5 Battalions Cargo Handling Multiplier 10
Parsons Type 228 Military Magneto-Plasma Drive (7) Power 228 Fuel Use 44.86% Signature 228 Exp 9%
Fuel Capacity 1,500,000 Litres Range 23.1 billion km (87 days at full power)
This design is classed as a Military Vessel for maintenance purposes
The main difference to your engines is that mine have a fuel use of 44.8%, whereas yours have one of a whooping 322% - Outch!
4.5 million liters to move your carrier less than 10 billion km? You _do_ have a crapload of fuel harvesters hanging around gas giants, I suppose
As for the concept of an assault carrier with FAC landing crafts:
While I see the appeal from a RP perspective (but then a lot more armor/passives should be on the FACs) I did away with the whole concept and just build 2 assault transports (6 to 8000 tons, heavy armor, space for a brigade) for each divisional transport and be done with it. No need to carry FACs around, twice the drop capacity, less fuel/maintenance needed,...
I mean look at it: You build a 26.000 ton ship, just to carry around 5 FACs with just one mission: To put 1 battalion on the ground each per run.
You build 31.000 tons of ships to do this.
You could just build a single 6.000 ton assault transport, that does exactely the same thing.
Hunt class Assault Transport 6,000 tons 63 Crew 855.6 BP TCS 120 TH 456 EM 360
3800 km/s Armour 6-29 Shields 12-300 Sensors 1/1/0/0 Damage Control Rating 1 PPV 0
Maint Life 0.5 Years MSP 89 AFR 288% IFR 4% 1YR 178 5YR 2671 Max Repair 108.3 MSP
Intended Deployment Time: 6 months Spare Berths 0
Drop Capacity: 5 Battalions
Parsons Type 228 Military Magneto-Plasma Drive (2) Power 228 Fuel Use 44.86% Signature 228 Exp 9%
Fuel Capacity 500,000 Litres Range 33.4 billion km (101 days at full power)
Vickers Type Delta/2.5 Electromagnetic Shield (5) Total Fuel Cost 75 Litres per hour (1,800 per day)
ECM 10
This design is classed as a Military Vessel for maintenance purposes
Same speed as your Chatham, heavy armor, some shields, ECM and the capability to land a brigade on a planet, all in one packet at a fraction of the cost of your Chatham.
If you realy want to stick with your assault carrier, I would at least do away with the troop transport bays on the Chatham and make it a true assault carrier, i.e. it carries the FACs and nothing else. The FACs take the troops from the Liberty and ferry them to the ground. This would allow you to either make the Chatham a lot smaller or carry a lot more FACs, so you can drop more troops in one go.
The Oil Company is a military design. Just pointing it out. You will need a 92.000 ton military shipyard to build it.
Not sure why you need troop transport bays on this one. Everything else seem commercial, so if you drop those, it should become a commercial vessel
I´d also reduce the deployment time on the Agincourts as I don´t think they will hang around outside the hangar bay for a quarter of a year
two weeks should be plenty.
That´s it for now