There are various systems which get lumped together as "proportional representation", though technically some of them aren't.

The simplest is where there is a single transferable vote - voters put the candidates in order of preference (or maybe pick their preferred three in order of preferance, in the London Mayoral version), and the ones at the bottom get eliminated, so the vote moves to the second choice, and so forth.

It means that the winning candidate is the one who is seen by most voters as best, or at any rate as least worst. Whereas under first-past-the-post it is perfectly possible (in fact it frequently happens) to get someone elected who is loathed by most of the voters, if their votes were distributed between two or more other candidates.

I'd imagine that a single transferable vote system would be quite compatible with the constitutional requirement you mentioned, art, since it does involve direct election. And it could make it easier for people to elect "the odd Socialist or Libertarian from time to time".