It may be a bit controversial, but I am still going to suggest it: What if barriers didn’t give points and clean sweep bonus when destroyed? This is mainly an idea to improve certain waves for daily and weekly challenges. As Orandza said, waves like Weakest Link are annoying, because to be able to compete in the challenges you have to waste huge amount of resources on destroying those damn barriers only to get points. I don’t think that’s quality gameplay.
IMO removing point rewards for barriers would just make challenges more fun to play. And would make waves like the Weakest Link, From Cover to Cover or Chicken Vending Machine much, much more enjoyable during the challenges. What’s better, with that solution we wouldn’t need to change those waves whatsoever. We are fighting chickens, not barriers after all…