Sandbox Mode

You can tell they are tinkering with an idea of a sandbox when they added siege mode and stuff like the "Flash Zone".

However, IMO if they create a sandbox it will just create more issues for glitches and gimmicks as players will be able to identify certain exploits if they were able to replicatethem a limitless amount of times opposed to being gated by cool downs. It's kind of a tit for tat. Considering they don't even fix major bugs in the PBE BEFORE releasing champs and skins to live. The team would just have a plethora of bugs.

They could call it "Sneaky's Sandbox".