Representatives and direct Taxes shall be apportioned among the several States which may be included within this Union, according to their respective Numbers, which shall be determined by adding to the whole Number of free PersonsTranslation: if the federal budget exceeds the revenues provided by duties on imports and excise taxes, then the state legislatures get the bill for the difference, with each state's share of the bill being calculated according to its share of the population.
To make this work, the Senate would once again need to be appointed by the state legislatures.
You have nailed it!
Abolish the income tax, rein the federal government back into the restraints of the Constitution, seat Senators through the respective state legislatures and never let the federal government out of that box again!