concept for a new item passive

I have an idea for an item with a passive that would reduce the cast time on abilities that have them. say the passive could make cast times 0.2 seconds shorter so an ability like ahri's q which has a very short cast time, only around 0.1 seconds, would benefit a lot and allow ahri to move instantly. then there would be another item with a passive that reduced cast times and channels by a percent and not a flat amount so something like a karthus ult would be casted 25% faster or something like that. one problem about that by reducing channel length is that it would also reduce how long abilities like master yi's meditate or fiddlesticks' drain last which is harmful instead of beneficial so the passive wouldn't affect abilities like that. I think it would be a really cool item as it could make it harder for enemies to react to something like thresh hook making it easier to land or maybe eliminate the cast time on ahri's q to get the full benefit of the extra movement speed