Note to self: if I ever get some fire imps I'm building at least four triple-decker fireball turrets outside my fort. One-tile turrets would be ideal for the best line of site, but I don't know how I'd safely contain the imps when I don't need them >.>
I AM SO DOING THIS.
Best way to contain would have them in a cave, attach a lever to the cage and to the floodgate.
Build a wall and a roof and a floor around them.
Have it like 1 tile
build it like so...
===
| I : )
===
L
l is lever
i is imp
| and = are walls
: is grate
) is flood gate.
man this is going to be perfect for me

, i have a open magma pipe and a LOT of imps and a magma man down there, should be fun, and not the fun (tm) kinda fun.
Also my previous projects before i found this was to create the goblin driving range or a goblin ball stadium.
Basically for the driving range
Have a giant tower that goes as high up as you can go, best if its on flatlands and not on mountains.
Have just tiles at the top and no walls.
Place a restraint there.
Put a goblin up on the restraint.
Order a single on duty macedwarf up to the tower.
ANd then the macedwarf if skilled enough wacks the goblin which then goes flying... in peices or otherwise.
Watch as they fall..
The same idea for the goblin driving range but underground and just 2 levels.
and have rotating macedwarfs.