I don’t really think he has a problem with changes in the consitution. There’s an ammendment process built in. It just seems quite often that it changes in other ways. I’d say some have had some pretty positive outcomes and clearly been right, but he’d (me, actually) prefer that changes are made through the ammendment process instead of just ignoring what it says.
As far as VAT goes, I personally don’t like it because it causes a crazy amount of record keeping, and I count that as a cost to business that is often left out of the discussion. It also makes the level of taxation harder to see for those who are actually being taxed.
A VAT system doesn’t require or presuppose a high level of taxation. You can have a VAT with a net 1% tax, or a VAT system with a net 50% tax.
As far as Paul goes, I don’t think he has, or would advocate for a VAT. He wants to remove the federal income tax. No doubts states will increase their income taxes when they see people with extra money and some services that need to be filled. At least at a state level, people have a much greater possibility of being included in conversations about tax levels and how those taxes are spent.