"Particle Emitter" part

Basically, it's a fully procedural thing which emits a picture as a particle, which would be a simple image repeated to create a particle or trail. It could be activiated by an AG, or a basic input (e.g. throttle)
Here are some settings that could be used for it:
-Particle Frequency: changes how much particles appear per second, low would result in small "puffs" while high would result in smooth trails, but also very laggy
-Particle Size: changes the size of the particle, obviously
-Particle Spread: works the same as guns' bullet spread in SP
-Image Used: lets you choose any available image, including some presets built into the game or a custom image (crafts which use innapropriate custom particles can just be removed by moderators)
-Transparency: self explanatory
-Emission: how much the particles glow
-Lifetime: how long the particles go for, in either seconds or meters from the craft
-Presets: simple presets such as "dense smoke", "wingtip trail", or "fire", etc. which adjust all of the above mentioned stuff