Variable game speed in custom matches

I had this idea for a potential training aid for players looking to learn how to evade skillshots more successfully, among other things. Basically, the overall speed of a custom game would be given a certain multiplier (50%, 100%, 125%, etc.). This would allow people to gradually work their way up to normal or heightened speed of overall gameplay during custom "training" matches, giving them the opportunity to learn how to evade skillshots in a more forgiving or harsher environment. I think this could help a lot of players in all brackets of play.

The idea behind this was brought on by spectating matches. It seemed like such a waste that people can only practice in real-time regardless of the scenario. I'd really like a League-based opportunity to work on my reflexes, so it could more easily translate into the actual game than other forms of reflex training.

Thanks for any and all feedback.