Expecting everyone to suddenly begin voluntarily giving up funds is where things must be changed gradually. That is why I suggested the flat tax and/or sales tax. I honestly don't know that the human animal has it in him to give enough voluntarily to support even the small government you imagine Issodhos. That is the flaw I keep running into, and the stumbling block that may be impossible to get over. Why insist on purity though? The system you are speaking of is a libertarian based society, not a Libertarian Utopia. Since we are all greedy beasts at heart I'm afraid at least some gentle coercion will always be required to keep the government coffers full. They wont be able to just print more money whenever they need it any more. Maybe a few generations down the road even those props could be kicked out from under the government.
"Be yourself; everyone else is already taken."— Oscar Wilde