Okay, let's get stupid.
The Good:
Twenty four heavy naval PPCs and eight Kraken-Ts in each arc for anti-shipping work, sixteen (each) naval lasers, subcapital lasers, subcapital cannons, and subcapital missile tubes in each arc for secondary anti-ship and anti-fighter defense. Naval C3 to coordinate fire with supporting units. Twelve laser AMS in each arc and thirty thousand double heat sinks meaning it can engage as many as seven hundred separate missile attacks simultaneously (or only around 150 if it is also firing EVERY OTHER GUN simultaneously), for the inevitable nuclear missile attacks. One hundred and eight fighters for air cover, fifty four small craft useful for boarding operations and over six hundred armored marines to stuff in those craft. Maintenance and repair capacity for a heavy cruiser and a pair of castrums, drone direction system able to handle an entire fleet of robotic drones. Better detection capability and faster than light communications. Leviathan level armor.
Minuses: It's a station, and no matter one's opinions on the cost calculations, It's a catastrophically expensive fixed defense system, and you're almost certainly using up resources that could have gone to building a more mobile and generally useful option. Honestly, unless you're just super dedicated to defending a single point in a single star system, this is probably really really dumb.
Gargantua System Defense Station
Mass: 2,500,000 tons
Technology Base: Inner Sphere (Experimental)
Introduced: 3145
Mass: 2,500,000
Battle Value: 416,787
Tech Rating/Availability: F/X-X-X-F
Cost: 97,818,685,000 C-bills
Fuel: 30,000 tons (75,000)
Safe Thrust: 0
Maximum Thrust: 0
Sail Integrity: N/A
Heat Sinks: 30000 (60000)
Structural Integrity: 1
Armor
Nose: 1401
Fore Sides: 1398/1398
Aft Sides: 1398/1398
Aft: 1400
Cargo
Bay 1: ARTS Fighter (108) 15 Doors
Bay 2: ARTS Standard Repair Facility (Unpressurized) (900,000)1 Door
Bay 3: Small Craft (56) 15 Doors
Bay 4: ARTS Standard Repair Facility (Unpressurized) (100,000)1 Door
Bay 5: ARTS Standard Repair Facility (Unpressurized) (100,000)1 Door
Bay 6: Cargo (358238.0 tons) 8 Doors
Ammunition:
9,600 rounds of Light SCC ammunition (4,800 tons),
4,800 rounds of Kraken (Tele-Operated) ammunition (480,000 tons),
9,600 rounds of Piranha ammunition (96,000 tons)
Dropship Capacity: 10
Grav Decks: 4 (1000 m, 1000 m, 1000 m, 1000 m)
Escape Pods: 0
Life Boats: 1,500
Crew: 189 officers, 369 enlisted/non-rated, 576 gunners, 280 bay personnel, 5000 passengers, 640 BA marines
Notes: Equipped with
1 Direct Tactical Analysis Control (DTAC) System (100 drones)
1 Naval Comm-Scanner Suite (Large)
1 Naval C3
1 Mobile Hyperpulse Generators (Ground-Mobile HPG)
8,393 tons of lamellor ferro-carbide armor.
Weapons: Capital Attack Values (Standard)
Arc (Heat) Heat SRV MRV LRV ERV Class
Nose (7,964 Heat)
4 Naval Laser 55 340 22(220) 22(220) 22(220) 22(220) Capital Laser
4 Naval Laser 55 340 22(220) 22(220) 22(220) 22(220) Capital Laser
4 Naval Laser 55 340 22(220) 22(220) 22(220) 22(220) Capital Laser
4 Naval Laser 55 340 22(220) 22(220) 22(220) 22(220) Capital Laser
4 Sub-Capital Laser /1 96 4(40) 4(40) 4(40) 0(0) Sub-Capital Laser
4 Sub-Capital Laser /1 96 4(40) 4(40) 4(40) 0(0) Sub-Capital Laser
4 Sub-Capital Laser /1 96 4(40) 4(40) 4(40) 0(0) Sub-Capital Laser
4 Sub-Capital Laser /1 96 4(40) 4(40) 4(40) 0(0) Sub-Capital Laser
4 Naval PPC (Heavy) 900 60(600) 60(600) 60(600) 60(600) Capital PPC
4 Naval PPC (Heavy) 900 60(600) 60(600) 60(600) 60(600) Capital PPC
4 Naval PPC (Heavy) 900 60(600) 60(600) 60(600) 60(600) Capital PPC
4 Naval PPC (Heavy) 900 60(600) 60(600) 60(600) 60(600) Capital PPC
4 Naval PPC (Heavy) 900 60(600) 60(600) 60(600) 60(600) Capital PPC
4 Naval PPC (Heavy) 900 60(600) 60(600) 60(600) 60(600) Capital PPC
4 Sub-Capital Cannon (Light) 48 8(80) 8(80) 8(80) 0(0) Sub-Capital Cannon
Light SCC Ammo (400 shots)
4 Sub-Capital Cannon (Light) 48 8(80) 8(80) 8(80) 0(0) Sub-Capital Cannon
Light SCC Ammo (400 shots)
4 Sub-Capital Cannon (Light) 48 8(80) 8(80) 8(80) 0(0) Sub-Capital Cannon
Light SCC Ammo (400 shots)
4 Sub-Capital Cannon (Light) 48 8(80) 8(80) 8(80) 0(0) Sub-Capital Cannon
Light SCC Ammo (400 shots)
4 Sub-Capital Missile Launcher (Piranha) 36 12(120) 12(120) 12(120) 0(0) Sub-Capital Missile
Piranha Ammo (400 shots)
4 Sub-Capital Missile Launcher (Piranha) 36 12(120) 12(120) 12(120) 0(0) Sub-Capital Missile
Piranha Ammo (400 shots)
4 Sub-Capital Missile Launcher (Piranha) 36 12(120) 12(120) 12(120) 0(0) Sub-Capital Missile
Piranha Ammo (400 shots)
4 Sub-Capital Missile Launcher (Piranha) 36 12(120) 12(120) 12(120) 0(0) Sub-Capital Missile
Piranha Ammo (400 shots)
4 Tele-operated Missile (Kraken T) 200 40(400) 40(400) 40(400) 40(400) Tele-Operated Capital Missile
Kraken (Tele-Operated) Ammo (400 shots)
4 Tele-operated Missile (Kraken T) 200 40(400) 40(400) 40(400) 40(400) Tele-Operated Capital Missile
Kraken (Tele-Operated) Ammo (400 shots)
12 Laser AMS 84 4(36) 0(0) 0(0) 0(0) AMS
FRS/FLS (7,964 Heat)
4 Naval Laser 55 340 22(220) 22(220) 22(220) 22(220) Capital Laser
4 Naval Laser 55 340 22(220) 22(220) 22(220) 22(220) Capital Laser
4 Naval Laser 55 340 22(220) 22(220) 22(220) 22(220) Capital Laser
4 Naval Laser 55 340 22(220) 22(220) 22(220) 22(220) Capital Laser
4 Sub-Capital Laser /1 96 4(40) 4(40) 4(40) 0(0) Sub-Capital Laser
4 Sub-Capital Laser /1 96 4(40) 4(40) 4(40) 0(0) Sub-Capital Laser
4 Sub-Capital Laser /1 96 4(40) 4(40) 4(40) 0(0) Sub-Capital Laser
4 Sub-Capital Laser /1 96 4(40) 4(40) 4(40) 0(0) Sub-Capital Laser
4 Naval PPC (Heavy) 900 60(600) 60(600) 60(600) 60(600) Capital PPC
4 Naval PPC (Heavy) 900 60(600) 60(600) 60(600) 60(600) Capital PPC
4 Naval PPC (Heavy) 900 60(600) 60(600) 60(600) 60(600) Capital PPC
4 Naval PPC (Heavy) 900 60(600) 60(600) 60(600) 60(600) Capital PPC
4 Naval PPC (Heavy) 900 60(600) 60(600) 60(600) 60(600) Capital PPC
4 Naval PPC (Heavy) 900 60(600) 60(600) 60(600) 60(600) Capital PPC
4 Sub-Capital Cannon (Light) 48 8(80) 8(80) 8(80) 0(0) Sub-Capital Cannon
Light SCC Ammo (400 shots)
4 Sub-Capital Cannon (Light) 48 8(80) 8(80) 8(80) 0(0) Sub-Capital Cannon
Light SCC Ammo (400 shots)
4 Sub-Capital Cannon (Light) 48 8(80) 8(80) 8(80) 0(0) Sub-Capital Cannon
Light SCC Ammo (400 shots)
4 Sub-Capital Cannon (Light) 48 8(80) 8(80) 8(80) 0(0) Sub-Capital Cannon
Light SCC Ammo (400 shots)
4 Sub-Capital Missile Launcher (Piranha) 36 12(120) 12(120) 12(120) 0(0) Sub-Capital Missile
Piranha Ammo (400 shots)
4 Sub-Capital Missile Launcher (Piranha) 36 12(120) 12(120) 12(120) 0(0) Sub-Capital Missile
Piranha Ammo (400 shots)
4 Sub-Capital Missile Launcher (Piranha) 36 12(120) 12(120) 12(120) 0(0) Sub-Capital Missile
Piranha Ammo (400 shots)
4 Sub-Capital Missile Launcher (Piranha) 36 12(120) 12(120) 12(120) 0(0) Sub-Capital Missile
Piranha Ammo (400 shots)
4 Tele-operated Missile (Kraken T) 200 40(400) 40(400) 40(400) 40(400) Tele-Operated Capital Missile
Kraken (Tele-Operated) Ammo (400 shots)
4 Tele-operated Missile (Kraken T) 200 40(400) 40(400) 40(400) 40(400) Tele-Operated Capital Missile
Kraken (Tele-Operated) Ammo (400 shots)
12 Laser AMS 84 4(36) 0(0) 0(0) 0(0) AMS
ARS/ALS (7,964 Heat)
4 Naval Laser 55 340 22(220) 22(220) 22(220) 22(220) Capital Laser
4 Naval Laser 55 340 22(220) 22(220) 22(220) 22(220) Capital Laser
4 Naval Laser 55 340 22(220) 22(220) 22(220) 22(220) Capital Laser
4 Naval Laser 55 340 22(220) 22(220) 22(220) 22(220) Capital Laser
4 Sub-Capital Laser /1 96 4(40) 4(40) 4(40) 0(0) Sub-Capital Laser
4 Sub-Capital Laser /1 96 4(40) 4(40) 4(40) 0(0) Sub-Capital Laser
4 Sub-Capital Laser /1 96 4(40) 4(40) 4(40) 0(0) Sub-Capital Laser
4 Sub-Capital Laser /1 96 4(40) 4(40) 4(40) 0(0) Sub-Capital Laser
4 Naval PPC (Heavy) 900 60(600) 60(600) 60(600) 60(600) Capital PPC
4 Naval PPC (Heavy) 900 60(600) 60(600) 60(600) 60(600) Capital PPC
4 Naval PPC (Heavy) 900 60(600) 60(600) 60(600) 60(600) Capital PPC
4 Naval PPC (Heavy) 900 60(600) 60(600) 60(600) 60(600) Capital PPC
4 Naval PPC (Heavy) 900 60(600) 60(600) 60(600) 60(600) Capital PPC
4 Naval PPC (Heavy) 900 60(600) 60(600) 60(600) 60(600) Capital PPC
4 Sub-Capital Cannon (Light) 48 8(80) 8(80) 8(80) 0(0) Sub-Capital Cannon
Light SCC Ammo (400 shots)
4 Sub-Capital Cannon (Light) 48 8(80) 8(80) 8(80) 0(0) Sub-Capital Cannon
Light SCC Ammo (400 shots)
4 Sub-Capital Cannon (Light) 48 8(80) 8(80) 8(80) 0(0) Sub-Capital Cannon
Light SCC Ammo (400 shots)
4 Sub-Capital Cannon (Light) 48 8(80) 8(80) 8(80) 0(0) Sub-Capital Cannon
Light SCC Ammo (400 shots)
4 Sub-Capital Missile Launcher (Piranha) 36 12(120) 12(120) 12(120) 0(0) Sub-Capital Missile
Piranha Ammo (400 shots)
4 Sub-Capital Missile Launcher (Piranha) 36 12(120) 12(120) 12(120) 0(0) Sub-Capital Missile
Piranha Ammo (400 shots)
4 Sub-Capital Missile Launcher (Piranha) 36 12(120) 12(120) 12(120) 0(0) Sub-Capital Missile
Piranha Ammo (400 shots)
4 Sub-Capital Missile Launcher (Piranha) 36 12(120) 12(120) 12(120) 0(0) Sub-Capital Missile
Piranha Ammo (400 shots)
4 Tele-operated Missile (Kraken T) 200 40(400) 40(400) 40(400) 40(400) Tele-Operated Capital Missile
Kraken (Tele-Operated) Ammo (400 shots)
4 Tele-operated Missile (Kraken T) 200 40(400) 40(400) 40(400) 40(400) Tele-Operated Capital Missile
Kraken (Tele-Operated) Ammo (400 shots)
12 Laser AMS 84 4(36) 0(0) 0(0) 0(0) AMS
Aft (7,964 Heat)
4 Naval Laser 55 340 22(220) 22(220) 22(220) 22(220) Capital Laser
4 Naval Laser 55 340 22(220) 22(220) 22(220) 22(220) Capital Laser
4 Naval Laser 55 340 22(220) 22(220) 22(220) 22(220) Capital Laser
4 Naval Laser 55 340 22(220) 22(220) 22(220) 22(220) Capital Laser
4 Sub-Capital Laser /1 96 4(40) 4(40) 4(40) 0(0) Sub-Capital Laser
4 Sub-Capital Laser /1 96 4(40) 4(40) 4(40) 0(0) Sub-Capital Laser
4 Sub-Capital Laser /1 96 4(40) 4(40) 4(40) 0(0) Sub-Capital Laser
4 Sub-Capital Laser /1 96 4(40) 4(40) 4(40) 0(0) Sub-Capital Laser
4 Naval PPC (Heavy) 900 60(600) 60(600) 60(600) 60(600) Capital PPC
4 Naval PPC (Heavy) 900 60(600) 60(600) 60(600) 60(600) Capital PPC
4 Naval PPC (Heavy) 900 60(600) 60(600) 60(600) 60(600) Capital PPC
4 Naval PPC (Heavy) 900 60(600) 60(600) 60(600) 60(600) Capital PPC
4 Naval PPC (Heavy) 900 60(600) 60(600) 60(600) 60(600) Capital PPC
4 Naval PPC (Heavy) 900 60(600) 60(600) 60(600) 60(600) Capital PPC
4 Sub-Capital Cannon (Light) 48 8(80) 8(80) 8(80) 0(0) Sub-Capital Cannon
Light SCC Ammo (400 shots)
4 Sub-Capital Cannon (Light) 48 8(80) 8(80) 8(80) 0(0) Sub-Capital Cannon
Light SCC Ammo (400 shots)
4 Sub-Capital Cannon (Light) 48 8(80) 8(80) 8(80) 0(0) Sub-Capital Cannon
Light SCC Ammo (400 shots)
4 Sub-Capital Cannon (Light) 48 8(80) 8(80) 8(80) 0(0) Sub-Capital Cannon
Light SCC Ammo (400 shots)
4 Sub-Capital Missile Launcher (Piranha) 36 12(120) 12(120) 12(120) 0(0) Sub-Capital Missile
Piranha Ammo (400 shots)
4 Sub-Capital Missile Launcher (Piranha) 36 12(120) 12(120) 12(120) 0(0) Sub-Capital Missile
Piranha Ammo (400 shots)
4 Sub-Capital Missile Launcher (Piranha) 36 12(120) 12(120) 12(120) 0(0) Sub-Capital Missile
Piranha Ammo (400 shots)
4 Sub-Capital Missile Launcher (Piranha) 36 12(120) 12(120) 12(120) 0(0) Sub-Capital Missile
Piranha Ammo (400 shots)
4 Tele-operated Missile (Kraken T) 200 40(400) 40(400) 40(400) 40(400) Tele-Operated Capital Missile
Kraken (Tele-Operated) Ammo (400 shots)
4 Tele-operated Missile (Kraken T) 200 40(400) 40(400) 40(400) 40(400) Tele-Operated Capital Missile
Kraken (Tele-Operated) Ammo (400 shots)
12 Laser AMS 84 4(36) 0(0) 0(0) 0(0) AMS
(I have attached the record sheet, which is still mostly useful even though the capital weapons hilariously overflow the space provided. Remember, all the arcs have the same weapons, so you can mostly get by with only one arc clearly listed)