For what you're doing I'd buy a fork lift mast. Just put elevator car on
forks. Bolted on, of course. Get a small electric hydraulic pump to run it.

For a safety from dropping; have you ever seen the catch on a car air bumper
lift? The unit won't go down unless you hold the lever down against spring
pressure. It's just a catch dog that will grab every inch or so.

Just a couple ideas.

Karl