My solution for this is a "Spiral Minecart with Airlock":
On the top level I have:
1) a collecting stockpile: a 3x3 stockpile without wheelbarrows that allows for up to 9 simultaneous haulers to collect plants.
2) a track stop: max friction, taking from the collecting stockpile and gets pushed/rode on being full or a certain number of days.
3) a minecart airlock: basically a pit in the middle of a 1x5 track, allows for the minecart to jump over the pit and continue it's route while breaking pathing for land units, this way you're sure no creature will ever use your minecart tracks as shortcuts or backdoors into your fort.
On the whatever middle levels I have:
1) a spiralling down parh for the minecart with it's tracks.
2) a spiralling up path with the necessary rollers.
On the bottom level I have:
1) a minecart airlock: just to avoid citizens and pets to wander into the spiral tunnels and get hit by a minecart.
2) a track stop; set to auto-dump onto:
3) a quantum stockpile: 1x1, set with no wheelbarrows and the proper items
So basically the minecart sits on the collecting track stop at the top, the haulers fill the collecting stockpile and load the minecart, then push/ride it, the minecart jumps over the top airlock pit, goes down the spiral path, jumps over the bottom airlock pit, passes over the dumping track stop, dumps everything on the quantum stockpile, and goes back up using rollers, to end up being friction-stopped by the collecting track stop, completing the loop.
Nothing is being dropped, so zero risk of killing by dropping.
The minecart paths should be completely enclosed and, with the pit airlocks, creatures shouldn't even have any reason or be able to physically path there, so zero risk of killing by minecart accidents.
Notice that the haulers on the top level are effectively cut-off from the main fortress, so you'll probably want to set up some living quarters (bed, chair, table, etc) and an inverse spiral system to deliver food and drink (and clothes if you just don't armour-dress them).