If there's absolutely no demand for the IRS then this "pet" is vanishingly small. No demand for the IRS? As in, everybody would trust everybody else not to try and free-ride?

There's a massive leap in everyone trusting everyone else, and people feeling like the best use of their money is to make sure other people give their money. Human psychology is relevant here.

I have to say, having now made a few comments on this: I think aspects of your idea might be doable or might work on a much smaller scale. It might be interesting to try this for a small town and see what happens, or to try it on a large scale with a fraction of tax money- both of these would not have many of the problems that people have raised with doing this on a very large scale. But as the plan stands there are too many problems for jumping to anything like the scale you want, and you aren't making the strongest case for your idea.