New game mode idea

I think a training type of game mode where players can practice their mechanics while playing against their friends or bots could be a great tool for people to improve skills that take a long time to master by just playing other game modes. Something like this could have things like free items to test out different builds, customizable/much shorter cool downs for practicing things like combos, flash timing, and ward jumping, as well as bots that can be be itemized however one wants. I think this could help eliminate a lot of frustration with oneself or their teammates for doing poorly or trying to learn difficult mechanics by playing pvp, especially since many skills in League take longer than just the few bot games many people are willing to put in. Anyone else agree, or know if Riot has ever considered doing something like this before?