By layering and federating, you introduce noise into the system. One layer may be controlled by one party, another by another. You are purposefully introducing noise and isolating possible corruption vectors. With enough noise and isolation, each time power switches over at a node or layer, there's widespread "corruption cleaning" that mostly involves running out all the corrupt guys from the other party and setting up your own corruption that works in a different way.
Looked at another way, the system has to have a way to be wrong. If one person or one party controls everything from top to bottom (or the system stops being layered and federated), then there's no feedback loop -- and there's your unholy nexus.
Personally I'd add term limits to the mix, mainly because I think whatever the government is, it should be understandable and controllable by an average citizen. Also if you're in for a long time, it's doubtful you'll change your ways -- and there goes the feedback loop again.
You never eliminate corruption. That's a fool's game. Instead what you want is to isolate it in such a way that over time it's easy to identify and remedy.