That is a major problem with it all. There is no such thing as a perfect political ideology. The corruption is inherent to society, for there will always be a segment of corrupt individuals. Even the small scale utopian communities fell to corruption. In my opinion the best solution would be to place power in as many hands as possible to try to mitigate the influence of corrupt individuals. Note that i'm not arguing for communism, because that usually ends up with a small group of government officials holding all the power.
But in that instance would anything ever get done? With power in the hands of the many, there will be so many differing opinions that I'm afraid the bureaucracy of that system would bring its downfall. Perhaps something along the lines of our Supreme Court? A council of sorts, but then that is done in Britain with their Parliament. More so of a Republic is what I'm thinking along the lines of.
How about E-democracy? It's a digital form of direct democracy, simple with today's technology. You could vote on your smart phone. It would increase vote turnout too.
Switzerland does a form of direct democracy if I'm not mistaken. I don't really have much information about how it works, but somehow I feel like we are too lazy and would not want to read all about the laws and things that are talked about every day in Congress.
I wouldn't defend something like the US supreme court. Lifetime appointments can be extremely bad. The problem with a republic is that it generally relies on majority rule. This can lead to subjugation, and possibly eradication, of any resistance. You are right though a system like what i'm describing would be horribly impractical, and more persuasive participants would form the ruling class.