"Wouldn't it be great to pay no Federal Taxes as long as you buy no Foreign goods if the Federal Government got all it's money for operating expenses from import Tariffs as allowed by the Constitution?"
Totally unworkable in practice. There is no way to set the tariff rate high enough to be revenue neutral without shutting down imports drastically. Then you would have to raise the rate exponentially to make up for the revenue shortfall, which would lead to (you guessed it) still higher rates.
One of the frequent FairTax opponents on FR, Willie Green, has advocated substituting import tariffs for corporate income taxes for several years. Even that limited measure won't work for the reasons mentioned above. Willie has been advocating that approach for several years and it wasn't even seriously entertained by the President's Tax Reform Commission, as far as I can see.
Reducing imports is another advantage, unless you believe having no duties on imports actually grows jobs here.
Of course it's not revenue neutral if you leave all of the unconstitutional BS in the mix...