If the PBE is for experimenting, why don't you try whacky stuff on it?
Every day could be a new, crazy idea that could be tried and tested for the sake of experimenting with new concepts!
Day 1: Make Caitlyn's traps invisible but destroyable, see what people think Day 2: Remove Zoe Day 3: Make Yi's Q last 1 whole second for the sake of a Duskblade/Lethality build Day 4: Remove Zoe Day 5: Let Varus's Q hone in onto champions/large monsters with max blight Day 6: Remove Zoe
Literally, the possibilities can be endless!