In light of the Republican version of tax reform, the tax plan that I would like to see is the one that returns the bulk of tax revenue to each state from where it was collected. The Federal government would keep enough revenue to fund national security; the State Department to conduct foreign affairs; the Justice Department to enforce the Constitution and the Bill of Rights; and a Department of Transportation and Interstate Commerce to maintain interstate highways and waterways, and to regulate civil aeronautics, and interstate commerce - involving anything moved from one state to another by any means including pipeline.
Everything else each state would fund and regulate according to the mandate of the citizens of the state and the financial ability of the state government based on the revenue collected from each state and subsequently returned by the Federal government. Maybe states could form voluntary cooperatives to address healthcare, pension funds, and other benefits that are valued by citizens and that would benefit from scale. I could see CA and WA States doing that because there is consensus in those two states regarding healthcare and pension funds.
Republicans should jump on the band wagon for such a tax plan. After all, it would validate two ideas dear to Republican hearts - local control and the elimination of the redistribution of wealth (I.e., that which occurs when the Federal government collects considerably more tax revenue from one state than it returns to the state in benefits - but instead redistributes some of the revenue to other states).