Possible "Gamemode" to let us test champions before buying them?

Yeah, I kind of figure that's what the free champion rotation is for, but sometimes don't come around as free for quite a while. I am proposing a very simple gamemode, kind of like a custom game with no rewards. Several times before I've bought champions that I thought might be cool only to be disappointed and instantly wish that I had bought another champion.

The new gamemode would allow you to test any of the 130ish champions in the game, but (as I stated before) with no rewards and bots only.

EDIT: It'd also be pretty nice if we were allowed to take a look at skins before buying them too.