Hey Edge, are you still working on those models? I'd really like to see this mod in action and from my hanging around at Relic News HW2 mod forums, i have learned a few encouragin things.
Sidewalls and Impellers are possible. For impellers, create a large disc shaped subsystem and place it where the impeller bands of a warship should be. Then texture this disc so that it would resemble the descriptions of an active impeller. Then make the impeller subsystem either invulnerable or just give it insane amounts of HP.
Sidewalls could be done similarily, altough they would be vertical discs and they could be damaged and they would be differently textured.
Laserheads are also possible. Simply make an unguided missile submunition that is so small it cant really be seen and give it a thin, bright, red trail. Then make the submunition very VERY fast.
Missile pods could be done IIRC.