People are forgetting to key things here, rich people, who buy a lot of stuff, expensive stuff, would finally have to pay full taxes. No tax breaks. S
Your 2nd point is valid, the evasion of such a tax would be more difficult than the evasion of Income Tax, in many instances.
Your 1st point however is a little more shaky.
Bearing in mind that I'm not 100% familiar with the US tax system, but viewing this from a more general perspective.
It's true what you say that 'rich' people who buy a lot of expensive stuff would pay more in Sales Tax if ST were increased, than they would if ST was not increased, but that does not mean that they would pay more in ST than they do currently in IT necessarily.
If a person earns $1m pa and pays 50% in IT they pay $500k; if the minimum cost of living is $20k, then that leaves him with $480k each year. Suppose he lives a life of luxury and spends $250k a year on 'luxuries', saving the remaining $250k.
Now lets take the same person a year later, after IT is done away with to be replaced with ST.
Income is still $1m, and his lifestyle doesn't change; to achieve the same tax revenue the ST would need to be 186%, leaving him with $330k to save. He's better off by $80k pa.
Now take a lower income, say $40k pa, IT @ 50% leaves them with $0 savings and no luxuries. ST @ 186% leaves them short by $17k pa
The only way the argument to abolish IT in favour of ST is to have variable rates of ST, but for every exemption, there has to be an increase at the top end, meaning the ST on luxury item would likely exceed 200%; as soon as a luxury item like a $500 smartphone starts to cost $1,500, a black market of buying via ebay.ca will mean you have even more people evading taxes than at present.
I think the best solution is a package of taxes, all kept a low as possible, on income, purchases and fees for registration and licenses where appropriate.
Whatever system, it needs to be simple, fair and practical.