This would have the advantage of cutting administration costs and would give the government a better idea of where to make cuts. It would also plug funding gaps as anyone working in the public sector would be able to see where specific funding is needed and divert their taxes accordingly. For example if a nurse has to work in unsanitary conditions, or if a soldier wants better equipment they could divert their taxes specifically towards those things. There should be some system put in place to ensure that overly wealthy individuals don't get to decide where the majority of taxes are spent but would also balence out to a degree as the majority of tax revenue comes from middle class earners.
Have all individually based taxes decided on where to be spent by the specific individual paying them.
Let each person specify on their tax return or online where thier specific individual taxes are spent, whether it be; education, healthcare, infastructure, defense, transport, energy, or any other area. This doesn't have to be limited to income tax and can be applied to any other individually based tax. Any other less popular areas could then be supported by non individually based taxes. It probably wouldn't work well with VAT and shouldn't apply to large private corporations but otherwhise would be a very good idea.