I'd really like to see the 5 attack speed gimmick come back eventually.
I know you removed it on Kog because it was really unhealthy with how his late game behaved and the on-hit items. However, I'd really like to see this gimmick come back, I hated Kog, but he was probably one of the most fun champions at the time in my opinion with the way kiting worked. He really felt like he was hard to become good with like the ADC equivalent of Riven.
I know it probably won't happen, but I really enjoyed this mechanic.