I may have an idea, but I'm not sure that dwarfs will like it !
I thought to a "slayer catapult" (dwarfs won't like to be thrown and servant may not want to send to death their fellows, that's why I said people won't like it

).
Instead of throwing stone blocks, the ammo can be slayers. BUT to not kill them, it can be a short range catapult. Different solution for the landed slayer :
- act as a fanatic (be killed after his damage) ;
- act as a doom-seeker (do his damage and stay alive) ;
- stay alive and act as a single unit ;
- maybe be killed on a misfire, something similar...
Edit : Oups, I just understand what you called a slayerpult... Sorry !
This can be an organ canon :
http://www.coolminiornot.com/97205
Edited by Xandar, 28 October 2011 - 11:11 AM.