Just had the idea that survivor should be re-introduced. It is great ds practice, but average performance matters so much more than peak performance. Hence the challenges isn't the best way to improve imo.
It was not very popular before, which is why it was removed. However, I believe that the main reason it wasn't popular was because it would take a minute and a half before it got interesting, so i got the idea of having a "levels" option when you create a survivor room. In that way it can be relevant for everyone to play, just start at a level just before it gets hard, and see who lasts the longest.