I got a hoist that lifts things via a wire rope. I have no safety issues lifting and lowering items because I can stay out of the way so if the hoist gives then it is a damage issue not a safety one.
However, once the item is hanging, I need to work under it. This is a safety concern. What I would like is to put in a mechanical inline wire rope clamp which could be opened during hoist operation and locked once the item is lifted. That way I would have a mechanical fix on the wire and hoist would just serve as a backup. The challenge is that for various reasons the clamp needs to be opened and closed easily, preferably with a one-handed operation (best if it involves pulling a lever). Does anyone make lever operated wire rope clamps?
The loads in question are small : 150 to 400 lb so this is why I think a simple inline clamp would work especially with hoist (rated at 1100 lb) as a backup.
I've been places where they used wire rope pullers for what you describe. They anchored the puller to the overhead structure and slipped the puller around the cable and then released tension on the hoist until the puller grabbed. My concern is you don't have any back-up safety to hold the load in case your one cable fails. Maybe some kind of floor jack or second lift point would suffice You should of course read and understand all safety requirements for the equipment you are using and follow the manufacturers instructions.