I think this will be rather "dangerous". I had some big problems with a few of our WCS-Missions, where suddenly shots gone through the enemy ships and made them invincible.
After many frustrating hours I found out, that I had to many objects in the mission area because of a asteroid-field that I made too big. After decreasing the number of the asteroids (by reducing the field size) the problem was fixed.
I guess, increasing the max numbers will be increasing the possibilty for this failure I guess, if there will be no raise to the max objects (subobjects ? ) per mission.
Unfortunately standard freespace asteroidsfields are good looking, but rather useless, since they do only very minor damage.
Since they aren't very dense even at 256 units (guess that's why you ask for it Topace), it would at least be better to give them much more damage potenial, and model a little bigger rocks.