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.