You can create a non-lethal multi z-level chute by adding retracting bridges every n z-levels (where n = 1 for perfect safety or n <= 5 for slight injuries to goblin-sized creatures). To automate the retracting of bridges in the correct order, you can use a parallel 2x1 chute with pressure plates set to activate when liquid level is above 0 and retracting bridges. Connect the pressure plate to the retracting bridges of both chutes on the same z-level. When you want to move creatures down the chute, simply drop some water into the parallel chute, and it will activate pressure plates, causing bridges to retract and both water and creatures to fall down a level - the process will repeat until the water and creatures reach the bottom of the chute.
Note that you'll need to either build a pump-stack to recycle the water or dispose of the old water and add new water when you want to use the system again.
Here's a side view for N = 3
WbWbpW Legend
W W W W = wall
W W W b = bridge
WbWpbW p = pressure plate
W W W
W W W
WbWbpW
Alternatively, you can create a 3x1 shaft with dwarf-activated pressure plates in the middle tile and up or down staircases (not up/down staircases) alternating between side tiles. Connect the pressure plates to retracting bridges in the main chute and put a lever at the bottom of the secondary shaft, then designate it to be pulled once - a dwarf will run down to pull it, triggering the bridges in the correct order.
Here's a side view for N = 3
WbW<p>W Legend
W W> <W W = wall
W W< >W b = bridge
WbW>p<W p = pressure plate
W W< >W < = up staircase
W W> <W > = down staircase
WbW<p>W