Training grounds?

An Idea for those who want to get gud. What if there were another game mode so to speak that allowed players to practice and or try out their ideas. Something a little more simpler than creating a custom and having to play through a regular game to just practice their last hitting. Im talking about a customizable instance where players can configure settings to to accommodate their need. For example: A player wants to practice last hitting so they'd set a single lane, where minions spawn instantly and infinitely. Maybe a player wants to try out a certain Build so they set the game where you instantly get sufficient gold and you can play against bots or friends. This could be used for testing, skill improvement, team practicing, or even just showing your friend a thing or two. I know that you can do all this in a normal custom game but it would just be more convenient and much faster with this. I would like to know others thoughts on this.