I didn't mean total replacement, in some cases it would work better, in other cases what we've got actually works pretty well. I meant some percentage of your tax should be controlled by the taxpayer directly, let's say 1% to start, increasing every 4 years by 1% up to, 20% for example.

I don't think 20% of the budget is capable of being discretionary. If you're really wanting to do so, some government agencies actually accept donations. When I sold my business, I donated to NASA. I couldn't earmark the donation for something like educational outreach as donations have to go into the general fund.