well I completed mission 4 without god mod on, but i did cheat:

Equipment:

Ship: Havoc light ancient fighter (why light? For the speed.)
Weapons: 4x Starburst, 1xHydra ML, 1x Doomsday ML, 1x Armaggedon torpedo, 2x ancient shield recharger, 1x ancient assault barrier, 1x ancient power enhancer, immortal essence, ancient light bioshield, lv4 scanner/tractor, order thruster.

5 shots with the armaggedon and the unity is down, taking any ships within a 500m radius with it.

Also, I had an issue with the "ultimate" missiles, they don't even hit fighters - they just explode behind them.

Once a freelancer, always a freelancer...