If you turn the cargo hatch, frameshift drive, fuel scoop and docking computer off you'll end up 0.03 MW below your max power output so everything runs fine. If you upgrade the life support to A and have it turn off when the weapons are out you can get another 1 MW to play with if you want to fly it that way (you'll have 25 minutes of 'guns out' time before you need to dock or suffocate

If you wanted to tweak it a bit you could change to burst or pulse lasers to save power and ramp up the defences or something but I find this build works extremely well for me : ) I'm loving it!