I would prefer a "slow debris" or "debris speed" flag that would go with the Object Editor. This would also be useful in conjunction with the "destroy before mission" flag to allow the player to come across ship debris, say in a nebula, without having the debris drift away from the area, or having to destroy the ship (self-destruct) during the mission and risk the explosion being visible. Something I'd also like to see, though it'd likely be much harder to do, would be to add a flag to make the debris of a ship, scannable. This would need to be limited to pieces above a certain size, but it would allow for some interesting possibilities in mission plots.
Later!