Pump mercury [or a safer dense liquid]?
If you still want a weight system then have a vessel as a weight and fill/empty it at the top/bottom of the drop and use a counterweight to return the vessel. Then you only need a small pump instead.
If you still want a weight system then have a vessel as a weight and fill/empty it at the top/bottom of the drop and use a counterweight to return the vessel. Then you only need a small pump instead.