Custom game, freedom

So I've tried out a bit of heroes of the storm and in a "custom game"(not really like the one in lol) you can reset cooldowns on your abilities an lvl up and level "down" as much at any time. It would be great if Riot took this idea in mind and made something similar in lol for the custom games. Where you can play a game and try out a build, and test different strats without having to level up for 20 minutes+, farm for gold and wait for your cooldowns to be back up. It would be really nice if you could change this stuff pre game, so you can play a "normal custom game" if you want. I know there is a lot threads and people with the same ideas or similiar, but I just wanted to freshen it up a bit :D.