Well you wanted a Budget Escort, and while I could have added a LFB that shoots the cost WAY up. Instead with have a lovely little do-it-all escort from the budget conscious Allied Conglomerate of Military Engineering... (think about that acronym for a moment in you need to)
Class/Model/Name: Zerstorer
Tech: Inner Sphere
Ship Cost: $4,526,046,004.00
Magazine Cost: $10,200,000.00
BV2: 37,808
Mass: 200,000
K-F Drive System: Compact
Power Plant: Maneuvering Drive
Safe Thrust: 3
Maximum Thrust: 5
Armor Type: Ferro-Carbide
Armament:
10 Capital Launcher Killer Whale
20 Naval Laser 45
36 Laser Large
56 AMS (IS)
24 LRM 20 (IS)
Class/Model/Name: Zerstorer
Mass: 200,000
Equipment: Mass
Drive: 36,000.00
Thrust
Safe: 3
Maximum: 5
Controls: 500.00
K-F Hyperdrive: Compact (6 Integrity) 90,500.00
Jump Sail: (3 Integrity) 40.00
Structural Integrity: 60 12,000.00
Total Heat Sinks: 1044(2088) Double 731.00
Fuel & Fuel Pumps: 20000 points 4,080.00
Fire Control Computers: 217.35
Armor: 276 pts Ferro-Carbide 240.00
Fore: 50
Fore-Left/Right: 46/46
Aft-Left/Right: 46/46
Aft: 42
Dropship Capacity: 0 0.00
Grav Decks:
Small: 2 100.00
Escape Pods: 20 140.00
Life Boats: 20 140.00
Crew And Passengers:
23 Officers in 1st Class Quarters 230.00
62 Crew in 2nd Class Quarters 434.00
46 Gunners and Others in 2nd Class Quarters 322.00
102 Bay Personnel 0.00
1st Class Passengers 0.00
2nd Class Passengers 0.00
50 Steerage Passengers 250.00
Bay #1 - Fighters (36) - 6 Doors
Bay #2 - Small Craft (6) - 1 Door
Bay #3 - Cargo (18567 Tons) - 1 Door
Small NCSS
Killer Whale Ammunition (150 Rounds) 7500 tons
AMS Ammunition (13440 Rounds) 1120 tons
LRM 20 Ammunition (1440 Rounds) 240 tons
Weapons Location Heat Damage Mass
2 Killer Whale Nose 40 80 (8-C) 300.00
2 NL 45 Nose 140 90 (9-C) 1,800.00
6 Laser Large Nose 48 48 (4.8-C) 30.00
7 AMS (IS) Nose 7 21 (2.1-C) 3.50
4 LRM 20 (IS) Nose 24 48 (4.8-C) 40.00
2 NL 45 FR 140 90 (9-C) 1,800.00
6 Laser Large FR 48 48 (4.8-C) 30.00
7 AMS (IS) FR 7 21 (2.1-C) 3.50
4 LRM 20 (IS) FR 24 48 (4.8-C) 40.00
2 NL 45 FL 140 90 (9-C) 1,800.00
6 Laser Large FL 48 48 (4.8-C) 30.00
7 AMS (IS) FL 7 21 (2.1-C) 3.50
4 LRM 20 (IS) FL 24 48 (4.8-C) 40.00
4 Killer Whale LBS 80 160 (16-C) 600.00
4 NL 45 LBS 280 180 (18-C) 3,600.00
7 AMS (IS) LBS 7 21 (2.1-C) 3.50
4 Killer Whale RBS 80 160 (16-C) 600.00
4 NL 45 RBS 280 180 (18-C) 3,600.00
7 AMS (IS) RBS 7 21 (2.1-C) 3.50
2 NL 45 AR 140 90 (9-C) 1,800.00
6 Laser Large AR 48 48 (4.8-C) 30.00
7 AMS (IS) AR 7 21 (2.1-C) 3.50
4 LRM 20 (IS) AR 24 48 (4.8-C) 40.00
2 NL 45 AL 140 90 (9-C) 1,800.00
6 Laser Large AL 48 48 (4.8-C) 30.00
7 AMS (IS) AL 7 21 (2.1-C) 3.50
4 LRM 20 (IS) AL 24 48 (4.8-C) 40.00
2 NL 45 Aft 140 90 (9-C) 1,800.00
6 Laser Large Aft 48 48 (4.8-C) 30.00
7 AMS (IS) Aft 7 21 (2.1-C) 3.50
4 LRM 20 (IS) Aft 24 48 (4.8-C) 40.00
End up with 15 missiles per Killer Whale tube, 20 tons of AMS ammo per gun, and 20 tons LRM ammo per launcher.
And I argue that this ship could do a passable job at all three roles you had in mind, without the need for variants.
EDIT: forgot the Small NCSS for added early detection capabilities.