I thought of a slightly milder version of the tax, which I call a land wealth tax. Fix a certain maximum value of land owned by a single person which would not be taxed. In theory this might be some quantile, like the 80th percentile of land value owned per person. (I'm pretty sure you would still be taxing the majority of land using this threshold! At least at first.) Then everything owned above that is taxed by value. This avoids a rebellion of the most vulnerable and sympathetic homeowners. Of course land owned through opaque ownership structures must be assumed to be above the limit. Corporations with transparent ownership structures might see their land divided up (a likely intractable math problem if you included publicly traded companies) or some approximation applied, or the land simply taxed.
One advantage of taxing land wealth versus wealth in general (a la Piketty) is that land — "real" property — is much harder to hide in offshore corporate holdings than general wealth. It is all documented by necessity.
I have no expectation, unlike George, that taxes on land could fully satisfy the general fund. But they could certainly play a significant part. A significant difficulty with land value taxes in general is the assessment of land value, which is a difficult problem and has caused controversy in the past due to fluctuations and apparent inconsistencies. My preferred approach in the United States would be a Constitutional Amendment, which would allow centralizing the necessary expertise with the resources of the federal government.
I like your creativity here but there have been actual calculations done around this and carving out provisions for tax exemptions is not necessary.
Pragmatically speaking, a land value tax would be rolled out first by replacing property taxes with land value taxes, and the majority of people come out far ahead at this stage because people live on lots that have been developed. It is underdeveloped lots that are losers in this phase.
A true georgist would not stop here though, and they would slowly continue to ramp up land value taxes, but rather than replacing property taxes, they would start lowering other taxes on productive activities such as sales taxes or income taxes. But this would be a slow transition.
Additionally, you would include provisions during this phase where tax payments could be deferred until the sale of the property in order to protect individuals who happened to purchase a home that has dramatically increased in value. This prevents situations where an older person might be forced out of their home due to higher taxes. The goal here would be to transition over the long term and protect people who invested significant amounts into their property. The rates would stay relatively low for quite some time. Having lower rates also solves issues that you mention around accuracy of assessments. If you only tax up to 33% of the rental potential of a property, then you can be off by literally a factor of 3 in an assessment and the land will still be profitable to utilize.
What you described ("minimum value that is not taxed...") is the definition of a step function. But yes, binned income brackets is also a form of means testing, and a poor way to design taxes.
One advantage of taxing land wealth versus wealth in general (a la Piketty) is that land — "real" property — is much harder to hide in offshore corporate holdings than general wealth. It is all documented by necessity.
I have no expectation, unlike George, that taxes on land could fully satisfy the general fund. But they could certainly play a significant part. A significant difficulty with land value taxes in general is the assessment of land value, which is a difficult problem and has caused controversy in the past due to fluctuations and apparent inconsistencies. My preferred approach in the United States would be a Constitutional Amendment, which would allow centralizing the necessary expertise with the resources of the federal government.