I think the only long term solution is a federal land and building tax. This is too important to leave to states (and definitely local) governments. A high tax with no credits, deductions, exemptions.

Then, from this tax, we can pay "forward" every adult tax payer (not children, only adults) a fixed amount that pays the cost of an imaginary nationwide median cost of a two bedroom unit. Only adults, all adults, regardless of whether you have no child or eight children. Must file a federal income tax return to qualify. Median nationwide cost somehow calculated and weighted by population, hopefully updated more than once a decade.

Everybody from Amazon.com to Walmart pays this land + building tax regardless of whether they are in Manhattan, New York or Deport, Texas. No exceptions.

Define land value.

This isn't hard: whatever a local assessor determines it to be, something they already have a lot of experience doing.

So this is basically a "your tax is whatever I deem it to be"?

Well yes but that's also the case with property taxes. A reasonable figure based on current market values seems simpler to calculate for unimproved land than it does for property tax, which includes the value of the unimproved land as well as everything else built or changed. And because it's the value of the _unimproved_ land it's based on, the value would be relatively stable over time as well as not varying much between one area and similar areas nearby, whereas property taxes are based on values that can change dramatically over time from one place to the next, which can lead to mis-valuations and general stress from constant changes.