Add a Seconds of CC to Champion Stats
Riot has stated that they are in favor of people "feeling like they are doing something" one of the simplest ways I can think of doing this for support roles is to add an amount of CC and maybe a Damage Shielded stat to end game stats. There is already a Healing Done, Damage Taken, even down to specifics like True Damage done and Largest Crit, all tracked by game stats. There is nothing to represent a Jana shielding X amount of damage, or a Sejuani stunning/slowing for X amount of time.
Adding these seems like a pretty simple addition to the end game detailed stats, and if implemented would easily grant a huge diversification in Fantasy leagues as Supports, and tanky Jungles and Tops no longer have to rely solely on assists for points.
Regardless of whether it is viable as a point addition to Fantasy, I feel like it would be a great way to increase the desirability of Support as a role in Solo Queue for players who feel like it is just a position about dealing with your team's vision.