I've never had any big problem with butchering.
I recently saw somewhere on the wiki that a workshop can butcher bodies within 43 tiles of the workshop. In addition to that, workshops can also butcher bodies stored in refuse piles anywhere (both fresh bodies of kills to yield meat etc, and old skeletons to yield bone).
Yup, keep a stockpile for
unrotten corpses somewhere nearby. The hard part is to protect it from vermin
and avoid exposure to miasma.
Bodies of sapients cannot be butchered, but if bones become available through "natural" butchering (such as severed arms from an axe) those bones can be used for bone based production
So... 10x Serrated Disc trap covereth a multitude of sins?
Butchering tame animals in cages is the same as butchery of any other tame animal, while wild caged creatures have to be killed in combat. I think you can dedesignate the creature from the cage to have it released (and possibly hurt the civilian releasing it), but the safer method is to build the cage and then hook it up to a lever and have a civilian pull the lever while the cage is surrounded by a militia squad.
See also:
Mass pitting. To prevent climbing, drop 2 levels down, no walls under the hatch... you know the drill.
If you want to make it more Dwarfy - add a water channel below in case of accidents... with two floodgates (pull corresponding lever to flush in the desired direction) - one leading to safety, another into 10x Serrated Disc traps, then sieve (floor grate), and access stairwell for collection of remnants and meatgrinder repair.