I just managed to squeeze in a nice little laser-equipped fighter, at fairly low tech levels.
Apollo class Fighter (P) 500 tons 23 Crew 85.1 BP TCS 10 TH 87 EM 0
8707 km/s Armour 1-5 Shields 0-0 HTK 3 Sensors 0/0/0/0 DCR 0 PPV 3
Maint Life 5.16 Years MSP 26 AFR 8% IFR 0.1% 1YR 2 5YR 24 Max Repair 43.75 MSP
Commander Control Rating 1
Intended Deployment Time: 3 days Morale Check Required
FAC Improved Nuclear Pulse Engine EP87.50 (1) Power 87.5 Fuel Use 401.06% Signature 87.50 Explosion 17%
Fuel Capacity 1 000 Litres Range 0.1 billion km (2 hours at full power)
10cm C3 Near Ultraviolet Laser (1) Range 16 000km TS: 8 707 km/s Power 3-3 RM 30 000 km ROF 5
Beam Fire Control R16-TS8000 (1) Max Range: 16 000 km TS: 8 000 km/s 75 50 25 0 0 0 0 0 0 0
Fighter Improved Pebble Bed Reactor R3-PB10 (1) Total Power Output 3 Exp 7%
Active Micro-Sensor AS10-R100 (1) GPS 160 Range 11m km Resolution 100
This design is classed as a Fighter for production, combat and planetary interaction
I managed to get a 0.1 HS sensor in, so it can spot its own targets, as well as a tiny engineering space so it can repair a laser failure on firing. Everything is squeezed to the bone to fit it all in (the exact size is 9.9908 HS), but it does work. Doesn't even need a reduced-size laser, either.
I think the loss of fighter-specific beam fire controls might not hurt as badly as we were afraid of. That BFC is 25% range, 200% speed = 12.5 tons. Even if I felt the need to jack it up to 4x speed, you can still fit that in a fighter.