What do you think about the new mechanic GROUNDING
Grounding for Cassiopeia? (prevents mobility abilities from being used) It is something I was waiting to be introduced in the game, I wonder if it will be used in other champs.
I also believe something like debuff that could reduce the effective range of movement abilites by a % fraction could also work.
Example (Cut Wings) in the link http://boards.na.leagueoflegends.com/en/c/skin-champion-concepts/Ysv2MAZp-s7-new-keystone-ideas-v-20