It requires continuous expansive improvements. It is like real world. Building a system robust to frauds works on the short term, but on the mid and long term is impossibile. That is why laws change, evolve, we have governments and so on. Because system reacts to your rules and algorithms, making them less effective.
And these continous expensive improvements are done daily, but it is a difficult job
Hydrogen and oxygen burn explosively. It wouldn’t last long