The best way to counteract inequality is by raising more
  revenue and then spending it on things that the middle and
  lower classes need, like national health insurance.

It ain't the job of the gubmint to "counteract inequality" in the economic sense (it's an impossible task in a free society, anyway)

  [The plan] also wrecks much of the political support for 
  tax expenditures...

When you think of lowered tax rates, tax credits and deductions as "tax expenditures", you've got it completely backwards. That money isn't the gubmint's money. If my salary were to be lowered by my employer, it's not an expenditure on my part like it is if I reduce my expendable income by investing in a CD.

  And perhaps most important, his plan gives the American  
  welfare state a much sturdier base for future expansion 
  (esp. since the VAT is less transparent than other forms 
  of taxation), especially since there's room here to add 
  some form of carbon tax, which is necessary for dealing 
  with global warming and would provide even greater 
  revenue going forward.

Oh yes, that's brilliant.

1. An expansion of the welfare state is a horrifically bad idea. A smaller welfare state is an advantage, in all kinds of ways: economically, demographically, and with respect to liberty and (little-r) republicanism.

2. Making the functions of government less transparent is a goal?

3. Carbon taxes are not necessary to "deal with global warming". Assuming that whatever part of global warming we actually have any ability to affect is significant enough to matter (evidence suggests otherwise, and in any case is far from settled), capitalist market responses would be vastly better at "dealing" with it than anything the gubmint could do with carbon tax revenues (which may not actually increase overall government revenues).

4. I hate the phrase "going forward".