Judging from Homeworld 2 screenshots, Relic has implemented the ability to expel debris clusters from a ship once a beam has impacted the ship.
Debris in HW2It's a thought for the Terran, Vasudan, and Shivan debris that are currently used as asteroids. (Plus, setting ships on autodestruct in the beginning of the mission creates more interesting debris.) These asteroid debris can be expelled from a damaged vessel only when a beam cannon hits its hull.
A flag in the weapons.tbl can do the job: "debris"
A constant can be used in FRED2 mission specifications to limit the number of generated debris.
If this idea has already been brought up, then throw your tomatoes at me!