I am convinced such a tax could be implemented, however, not under the current US campaign finance system.  A large loophole would certainly be inserted.  It is the same problem with every legislative attempt to reduce tax  "avoidance" by the upper income brackets--convincing >50% of legislators to simultaneously bite the hands that feed them.  Tall order, but it would be a wonderful spectacle!

As the Dutch said while fighting the Spanish: "It is not necessary to have hope in order to persevere."