every app wanted to have its own persistent notification
When? Which apps? I've been using Android since KitKat and I only remember persistent notifications by apps that needed them (to keep working, stay in memory).
That said, I agree that a permission would be nice, as I am skeptical of the use cases shown in the article mockups. I think it should stay an ongoing notification thing as anything else would indeed take more space.
So it took 4 major releases to make the quick settings reasonable again... I'm actually glad most other OEMs did not follow when Google did the change in 12.