Put an engine 3 on a fighter and nothing else. Speed should be around 5.5+. (6.2 for Rebels).
Deploy 1-3 squadrons of them.
Watch as the AI fires weapons and sends fighters after them. Generally messing up their fleet. At 4x game speed it makes for a nice whirlwind of fighters.
Bombard the enemy with long range weapon ships.
At the post battle report, see that the decoy fighters have 0% hits on them.
This needs rebalancing so that the fighters can be destroyed. Possibly make it so that anti-fighter lasers eventually get an automatic hit. Or even add a new ‘Flak Cannon’ weapon with a small area of effect damage. The little smoke explosions in space would make for good visuals. Flak cannons were featured in the classic space combat game ‘Freespace 2’.
As a quicker fix, make it so that fighters without weapons are completely ignored by ships.