Your scenario is unrealistic because real humans aren't that tightly clustered, so you get defectors. And people vote strategically. The winning position is the centroid.
It is not known whether proportional representation can compete with the best single winner voting methods. We don't have enough data and we can't do multi-winter Bayesian regret calculations confidently. Here's an article you really should read if you think proportion representation is the answer.
https://rpubs.com/Jameson-Quinn/VSE5key
Your scenario is unrealistic because real humans aren't that tightly clustered, so you get defectors. And people vote strategically. The winning position is the centroid.
https://www.rangevoting.org/AppCW
It is not known whether proportional representation can compete with the best single winner voting methods. We don't have enough data and we can't do multi-winter Bayesian regret calculations confidently. Here's an article you really should read if you think proportion representation is the answer.
https://www.rangevoting.org/PropRep