I think I don't like this idea for the wrong reason.

Making sales tax less regressive would be a good thing.

The implementation difficulties don't bother me per se; I think what's making me not like this idea is that it wouldn't do much for wealth disparity. If you're Wealthy with a capital W, you don't really spend that much, compared to your income.

But even if I'm also interested in tax policies to decrease the accumulation of massive amounts of wealth and the accompanying power in the hands of a single individual, I shouldn't dislike a tax policy that would do a different good thing -- if it could be implemented -- just because it doesn't do the other thing I want.

> I think what's making me not like this idea is that it wouldn't do much for wealth disparity. If you're Wealthy with a capital W, you don't really spend that much, compared to your income.

These problems can be solved via extremely high estate taxes or property taxes.

Yes, but a marginal sales tax is impossible to enforce. Countries that do have sales taxes usually have a "normal" rate and several tiers of reduced rates for food and essential goods. E.g. in Italy the VAT rate is 22%, but some listed goods and services are instead taxed 10%, 4% or 0%.