I hear you, and I can sympathize as someone who has lived in cities that have changed rapidly. However, I can see a long-term venture fund taking the exact bet

I hear you, and I can sympathize as someone who has lived in cities that have changed rapidly. However, I can see a long-term venture fund taking the exact bet you suggested. If the value of the new building that combines parcels is high enough, there is no way a land value tax would address your desire to stop landlords from waiting for opportune development projects. What you would like is a punitive vacancy tax, perhaps combined with a required sale after a certain amount of vacancy. My ultimate question is why you might want this. A land value tax is supposed to encourage the highest and best use of a parcel. This developer recognized that the highest and best use of a parcel might actually include the use of adjacent parcels. Shouldn't we encourage this?