What I did was as follows:
Create a room in which most of the floor was channeled out and replaced with grates. You can't make the entire floor out of grates because each grate needs to be supported by one adjacent solid floor or wall tile, but you can make most of it open. Underneath the grates dig out a drainage channel leading away to an underground river, chasm, or map-edge fortification drain. On the floor tiles you had to leave solid place a statue, an armor stand or weapon rack, and beds. Designate this region as a meeting area, barracks, and statue garden.
Above the grated meeting room dig another room with a floor area approximately equal to the area of all the grates put together. Channel out the floor, leaving only one tile on the side solid. Cover the open floor area with a retracting bridge. On the one solid non-bridge-covered square place a pressure plate that activates for water level 7/7, and link it to the bridge.
Open a channel from the bridge room on the side opposite the pressure plate to a nearby river, aquifer, or other water source. The water will begin filling the room. When the room completely fills to 7/7, the bridge will open and dump all the water on the meeting/party/barracks room below. Those dwarves will begin drowning and cancel their partying and sparring, but the water should immedately drain out through the grates and draining channels below them. Then the bridge will close and the water will start to refill the bridge room. This repeats forever.
This requires only one bridge linked to one pressure plate, and no other power so long as you have a source of water at least 3 levels above the bottom of the map. The one I built had the arrangement on the surface with the water being pumped up from belowground, but if you can build the whole thing below the water you can make it gravity-fed. And it repeats forever automatically without requiring any lever-pulling. You will get a FPS drain every time it activates from the water movement, and a lot of sparring and attend party job cancellation spam as well.
I haven't tested the design for putting out flaming dwarves, but it should do that. I build this device to train all my dwarves in swimming, and give them happy thoughts from water mist. I also hoped it would wash off the blood/vomit/mud/whatever coating they all carry, but water doesn't seem to do that in the current version.