Crane counterweights are a completely different matter. The crane doesn't have to drop the counterweight to take on load (the opposite really, unless it's a superheavy with active counterweighting the entire point is to be more stable once loaded).
So the issue with this thing is, any time you move an actual load from A to B, you need to have a weight waiting for you at point B. Or to offgas at which point you won't be able to make a second trip without regassing.
If the weights remain on the ground you can use a pulley system to load and unload weight, just put slack in the cable and lighten the load… Could even be automated with the right sensors.
So the issue with this thing is, any time you move an actual load from A to B, you need to have a weight waiting for you at point B. Or to offgas at which point you won't be able to make a second trip without regassing.