I still maintain that a dropship and PWS are more effective in this sort of role. Still, I've designed a...thing. About half the listed maximum weight, loaded down with cheap AMS systems because look, all you need to do is make sure the enemy can never hit you with a PWS' missile armaments.
Chidori Patrol Ship
Mass: 120,000 tons
Technology Base: Inner Sphere (Advanced)
Introduced: 3145
Mass: 120,000
Battle Value: 17,331
Tech Rating/Availability: E/X-X-X-F
Cost: 3,987,490,000 C-bills
Fuel: 11,000 tons (55,000)
Safe Thrust: 4
Maximum Thrust: 6
Sail Integrity: 3
KF Drive Integrity: 5
Heat Sinks: 485
Structural Integrity: 40
Armor
Nose: 21
Fore Sides: 18/18
Aft Sides: 16/16
Aft: 11
Cargo
Bay 1: Small Craft (2) 1 Door
Bay 2: Fighter (10) 2 Doors
Bay 3: Cargo (10073.0 tons) 1 Door
Ammunition:
960 rounds of Anti-Missile System [IS] ammunition (8 tons),
240 rounds of Light SCC ammunition (3 tons),
66 rounds of Piranha ammunition (660 tons)
Dropship Capacity: 0
Grav Decks: 1 (100 m)
Escape Pods: 0
Life Boats: 0
Crew: 28 officers, 41 enlisted/non-rated, 42 gunners, 30 bay personnel
Notes: Mounts 96 tons of standard aerospace armor.
Weapons: Capital Attack Values (Standard)
Arc (Heat) Heat SRV MRV LRV ERV Class
Nose (32 Heat)
3 Sub-Capital Missile Launcher (Piranha) 27 9(90) 9(90) 9(90) 0(0) Sub-Capital Missile
Piranha Ammo (33 shots)
5 Anti-Missile System 5 2(15) 0(0) 0(0) 0(0) AMS
Anti-Missile System Ammo [IS] (120 shots)
FRS/FLS (125 Heat)
2 Sub-Capital Cannon (Light) 24 4(40) 4(40) 4(40) 0(0) Sub-Capital Cannon
Light SCC Ammo (40 shots)
4 Sub-Capital Laser (SCL/1) 96 4(40) 4(40) 4(40) 0(0) Sub-Capital Laser
5 Anti-Missile System 5 2(15) 0(0) 0(0) 0(0) AMS
Anti-Missile System Ammo [IS] (120 shots)
RBS/LBS (125 Heat)
2 Sub-Capital Cannon (Light) 24 4(40) 4(40) 4(40) 0(0) Sub-Capital Cannon
Light SCC Ammo (40 shots)
4 Sub-Capital Laser (SCL/1) 96 4(40) 4(40) 4(40) 0(0) Sub-Capital Laser
5 Anti-Missile System 5 2(15) 0(0) 0(0) 0(0) AMS
Anti-Missile System Ammo [IS] (120 shots)
ARS/ALS (125 Heat)
2 Sub-Capital Cannon (Light) 24 4(40) 4(40) 4(40) 0(0) Sub-Capital Cannon
Light SCC Ammo (40 shots)
4 Sub-Capital Laser (SCL/1) 96 4(40) 4(40) 4(40) 0(0) Sub-Capital Laser
5 Anti-Missile System 5 2(15) 0(0) 0(0) 0(0) AMS
Anti-Missile System Ammo [IS] (120 shots)
Aft (32 Heat)
3 Sub-Capital Missile Launcher (Piranha) 27 9(90) 9(90) 9(90) 0(0) Sub-Capital Missile
Piranha Ammo (33 shots)
5 Anti-Missile System 5 2(15) 0(0) 0(0) 0(0) AMS
Anti-Missile System Ammo [IS] (120 shots)
ETA: Oh my god it's morning and I've realized how badly under-equipped this thing is to have actual immunity to Mule PWS fire. I don't need 4-5 AMS to neutralize Killer whale fire, I think I need 16-48 depending on if I expect to take all the waves in the same arc. I'm still not using Laser AMS because heat and expense.
Chidori II Patrol Ship
Mass: 120,000 tons
Technology Base: Inner Sphere (Advanced)
Introduced: 3070
Mass: 120,000
Battle Value: 21,132
Tech Rating/Availability: E/X-X-F-F
Cost: 4,005,088,000 C-bills
Fuel: 11,000 tons (55,000)
Safe Thrust: 4
Maximum Thrust: 6
Sail Integrity: 3
KF Drive Integrity: 5
Heat Sinks: 485
Structural Integrity: 40
Armor
Nose: 21
Fore Sides: 18/18
Aft Sides: 16/16
Aft: 11
Cargo
Bay 1: Small Craft (2) 1 Door
Bay 2: Fighter (10) 1 Door
Bay 3: Cargo (9216.0 tons) 1 Door
Ammunition:
3,072 rounds of Anti-Missile System [IS] ammunition (8 tons),
144 rounds of Light SCC ammunition (3 tons),
60 rounds of Piranha ammunition (310 tons)
Dropship Capacity: 0
Grav Decks: 1 (100 m)
Escape Pods: 0
Life Boats: 0
Crew: 28 officers, 41 enlisted/non-rated, 42 gunners, 30 bay personnel
Notes: Mounts 95 tons of standard aerospace armor.
Weapons: Capital Attack Values (Standard)
Arc (Heat) Heat SRV MRV LRV ERV Class
Nose (43 Heat)
3 Sub-Capital Missile Launcher (Piranha) 27 9(90) 9(90) 9(90) 0(0) Sub-Capital Missile
Piranha Ammo (30 shots)
16 Anti-Missile System 16 5(48) 0(0) 0(0) 0(0) AMS
Anti-Missile System Ammo [IS] (384 shots)
FRS/FLS (136 Heat)
2 Sub-Capital Cannon (Light) 24 4(40) 4(40) 4(40) 0(0) Sub-Capital Cannon
Light SCC Ammo (24 shots)
4 Sub-Capital Laser (SCL/1) 96 4(40) 4(40) 4(40) 0(0) Sub-Capital Laser
16 Anti-Missile System 16 5(48) 0(0) 0(0) 0(0) AMS
Anti-Missile System Ammo [IS] (384 shots)
RBS/LBS (136 Heat)
2 Sub-Capital Cannon (Light) 24 4(40) 4(40) 4(40) 0(0) Sub-Capital Cannon
Light SCC Ammo (24 shots)
4 Sub-Capital Laser (SCL/1) 96 4(40) 4(40) 4(40) 0(0) Sub-Capital Laser
16 Anti-Missile System 16 5(48) 0(0) 0(0) 0(0) AMS
Anti-Missile System Ammo [IS] (384 shots)
ARS/ALS (136 Heat)
2 Sub-Capital Cannon (Light) 24 4(40) 4(40) 4(40) 0(0) Sub-Capital Cannon
Light SCC Ammo (24 shots)
4 Sub-Capital Laser (SCL/1) 96 4(40) 4(40) 4(40) 0(0) Sub-Capital Laser
16 Anti-Missile System 16 5(48) 0(0) 0(0) 0(0) AMS
Anti-Missile System Ammo [IS] (384 shots)
Aft (43 Heat)
3 Sub-Capital Missile Launcher (Piranha) 27 9(90) 9(90) 9(90) 0(0) Sub-Capital Missile
Piranha Ammo (30 shots)
16 Anti-Missile System 16 5(48) 0(0) 0(0) 0(0) AMS
Anti-Missile System Ammo [IS] (384 shots)
And for True All-Around Immunity...
Chidori III Patrol Ship
Mass: 120,000 tons
Technology Base: Inner Sphere (Advanced)
Introduced: 3070
Mass: 120,000
Battle Value: 32,192
Tech Rating/Availability: E/X-X-F-F
Cost: 4,056,288,000 C-bills
Fuel: 11,000 tons (55,000)
Safe Thrust: 4
Maximum Thrust: 6
Sail Integrity: 3
KF Drive Integrity: 5
Heat Sinks: 485
Structural Integrity: 40
Armor
Nose: 21
Fore Sides: 18/18
Aft Sides: 16/16
Aft: 11
Cargo
Bay 1: Small Craft (2) 1 Door
Bay 2: Fighter (10) 1 Door
Bay 3: Cargo (7822.0 tons) 1 Door
Ammunition:
9,216 rounds of Anti-Missile System [IS] ammunition (768 tons),
144 rounds of Light SCC ammunition (72 tons),
60 rounds of Piranha ammunition (600 tons)
Dropship Capacity: 0
Grav Decks: 1 (100 m)
Escape Pods: 0
Life Boats: 0
Crew: 28 officers, 41 enlisted/non-rated, 42 gunners, 30 bay personnel
Notes: Mounts 95 tons of standard aerospace armor.
Weapons: Capital Attack Values (Standard)
Arc (Heat) Heat SRV MRV LRV ERV Class
Nose (75 Heat)
3 Sub-Capital Missile Launcher (Piranha) 27 9(90) 9(90) 9(90) 0(0) Sub-Capital Missile
Piranha Ammo (30 shots)
48 Anti-Missile System 48 14(144) 0(0) 0(0) 0(0) AMS
Anti-Missile System Ammo [IS] (1152 shots)
FRS/FLS (168 Heat)
2 Sub-Capital Cannon (Light) 24 4(40) 4(40) 4(40) 0(0) Sub-Capital Cannon
Light SCC Ammo (24 shots)
4 Sub-Capital Laser (SCL/1) 96 4(40) 4(40) 4(40) 0(0) Sub-Capital Laser
48 Anti-Missile System 48 14(144) 0(0) 0(0) 0(0) AMS
Anti-Missile System Ammo [IS] (1152 shots)
RBS/LBS (168 Heat)
2 Sub-Capital Cannon (Light) 24 4(40) 4(40) 4(40) 0(0) Sub-Capital Cannon
Light SCC Ammo (24 shots)
4 Sub-Capital Laser (SCL/1) 96 4(40) 4(40) 4(40) 0(0) Sub-Capital Laser
48 Anti-Missile System 48 14(144) 0(0) 0(0) 0(0) AMS
Anti-Missile System Ammo [IS] (1152 shots)
ARS/ALS (168 Heat)
2 Sub-Capital Cannon (Light) 24 4(40) 4(40) 4(40) 0(0) Sub-Capital Cannon
Light SCC Ammo (24 shots)
4 Sub-Capital Laser (SCL/1) 96 4(40) 4(40) 4(40) 0(0) Sub-Capital Laser
48 Anti-Missile System 48 14(144) 0(0) 0(0) 0(0) AMS
Anti-Missile System Ammo [IS] (1152 shots)
Aft (75 Heat)
3 Sub-Capital Missile Launcher (Piranha) 27 9(90) 9(90) 9(90) 0(0) Sub-Capital Missile
Piranha Ammo (30 shots)
48 Anti-Missile System 48 14(144) 0(0) 0(0) 0(0) AMS
Anti-Missile System Ammo [IS] (1152 shots)