Of the methods you presented, I felt donations will have the slightest impact or effectiveness. However you are spot on in writing that "If something is really needed, then it will be funded. If it’s not needed, then it should be abolished anyway." Incentives are key and combining the nature of running a public service with the interests of a decentralized profit generating entity would be ideal. Maybe we can throw everyone's interest into a blender and mix them up so all have a more concrete stake in the whole system? Meshing the features and future of blockchain with our lives will sidestep the need for most governing activities (through its transparent and trustless nature) or drastically improve the efficiency of continuing social organizational methods. Allocation of funds and reward for good behavior stand to be revolutionized if the liberation of value and money continues to happen. In that world even simple donations can have a unimagined impact (take for instance, the funding of the Sanders political campaign in the USA).

I refer to this image from Unchained Capital to, hopefully, help illustrate the point.