Training Grounds or Arena

I'm new to the boards so sorry if this is in the wrong category. As I'm sure im not the first one. I would like to have a Training Grounds or a Training Arena, here you can test out any champion without having to purchase them. You can see how well you battle with them as well. I was thinking the players would be able to switch from character to character with a button or a chart somewhere on the screen. You'd be able to enter a Build and Test mode, In Build mode you'd be able to place down any bots, place down nexus', turrets and really just build your own map to test your champion on. This way you don't have to be the one that causes the team to lose the game on a PvP or a Co-Op vs AI game. This way you can enjoy it by yourself instead of having other players suffer through your champion testings. This is just a thought feel free to add on as well :)