While I myself would make a wonderful monarch and encourage you all to nominate me as your king or queen, sadly I am not immortal and the problem you describe is a real one.

I personally think the solution may be to remove the idea of representation from government, because the perverse incentives for anyone at a structural node are tempting and human nature is fragile. You can try to engineer corruption and rent-seeking with rule systems, but as we've seen in many Communist countries taking money out of things doesn't necessarily get your a more equitable or sustainable society.

I see a future with a much abridged legal code that is maintained somewhat like Wikipedia or a version control system, and whose implementation is built around blockchain technology and a narrowly-defined ethical calculus. However I can only handwave this for the time being as the challenges of computation legal and governmental systems are non-trivia, not to mention offering the many novel problems that would surely ensue.