Hey, I havn't been around for a while, but I'm extremly excited about the progress made during this time! It looks like Dwarf Fortress remains the best game ever created, with still infinite potential for improvement!
So, having that out of the way, my suggestion is: (Pardon me, if it's already in and I just don't know
)
Automatic artillery that self-loads and possibly shoots, using the power of a wind or water turbine, which would redefine the meaning of a Gattling siege engine.
The up-side would be increased rate of fire to insane levels and no operator required.
The down-side would be the insane ammount of ammunition required, and close to zero accuracy.
The rate of fire could depend on the amount of power transefered to the engine and quality of over-all parts of the system.
The question is, how would the ammunition be handled, since as it stands, the operator needs to place it inside from his/hers/its inventory into the engine.
It could be either stockpiled inside the siege engine, or the system could require another building that would hold and load the ammunition, requiring more power.
If the latter option would have been chosen, the loading building would have to be placed next to the siege engine, and connected via mechanisms, rendering the siege engine orientation-dependant, if automated reloading was to retain it's functionality. So it could fire only in the direction in which the entire system was built.