A wide range of political opinion is sometimes useful (e.g. in one of the houses of a legislative body). Moderate candidates are also useful. Rather than choose

A wide range of political opinion is sometimes useful (e.g. in one of the houses of a legislative body). Moderate candidates are also useful. Rather than choose one voting system to use for everything, it might be appropriate to use a couple voting systems that have different strengths and weaknesses. So you might imagine one house of a legislature elected with approval voting, and a different house elected with a proportional method.