At the risk of sounding pedantic: how do you prevent a capitalist economy, an inherent cumulative system that in practice can not be separated from the meta-system that regulates it, from turning into cronyism?
I suspect you're looking for some sort of iron clad algorithmic solution that is good for all cases, that's not how it works. The answer is the same as always: eternal vigilance. An educated and engaged electorate. A functional media. And the ability of the government to course correct as necessary. Institutions that feel they are accountable to the will of the electorate. There are, of course, many examples of this not working, but there are examples of it working as well (trust busting around the turn of the 20th century, the breakup of ma-bell, etc.)
