Sandbox mode?

They have given reason in the past as to why they will not make a sandboxmode.

yeah thats a really good idea. There have been tons of times where I wanted to test runes, test things at level 6 but never bothered because it took too much work.

and no cooldowns

I feel like the problem with a sandbox mode is that it lacks 1 key factor in a LoL game: Progression.

Most builds shouldn't be, "I'mma by X item, then Y item, then Z item, etc.", but should evolve naturally over the course of a game. Each item choice shouldn't be about that is the best item statistically, but what is the best item for the situation. Sandbox mode would be LoL in a vacuum and that will only really get you so far.