It makes me wonder, now that cryptocurrency is a thing, if fiscal policy could be embedded directly in the monetary system. Rather than a separate tax that's charged and remitted to the treasury, it'd simply be the difference between what a consumer spends and what a producer receives, much like how transaction fees come straight out of the transaction.
Effectiveness of UBI is still an area of much debate and research. Early results of this research based on a few pilots is decidedly not positive.
They pose major problems in terms of tax fairness though. The reason for this is that VAT efects the poorer disproportionately (poor people spends almost 100% of their income, while richer people won't spend a larger fraction of their revenue) while LVT targets the middle class (AKA those that don't have enough capital to diversify their assets and invest beyond their home).
Economists have known for 100 years that land value taxes (LVT) are by far the most efficient way to raise taxes. After that consumption taxes are the next most efficient. Corporate taxes and taxes on investment income are one of the least efficient, most distortionary, forms of taxation.
Yet policymakers and voters show no sign of changing their opinions, despite how much economic evidence continues to pile up. LVTs are extremely unpopular, because home ownership is fetishized by the middle class as a vehicle for wealth accumulation. Even in progressive polities like California, there's always tremendous political will to keep residential property taxes artificially low.
VAT taxes are almost just as despised, especially in America. Meanwhile higher corporate and investment taxes are supported by large majorities. Despite the fact that they impose serious drags on productivity and growth. If your goals is having a more progressive tax code or increasing income equality, the much better strategy is to combine high LVT/VAT taxes with a UBI, rather than explicitly try to target poorly designed tax schemes at rich people.