I have an idea that can be a good buff for Garen. Kind of like a mini rework. Have Garen's Q interact with his other abilities similiar to how Ryze's E works.
So using Q normally will result in a 1 second silence (the silence duration does not increase by level). Using Q + W will make Garen immune to all kinds of CC for 1 second. Q + E will give his silence an AOE effect. Using Q + R will result in an one second AOE fear to everyone caught in the radius of the shockwave if the execute was succesful and a two second AOE fear if Garen succesfully executed the villian.
Now Garen has more soft CC, a defensive ability that can help him engage as well as hard CC in his ult. All his effects last only 1 second (max 2 seconds if he used his ult effectively). I also think that all his CDs are okay with the exception of his R. His R cooldown can be buffed or nerfed depending on how strong Riot feels this kit would be.
Now Garen can add value to a teamfight. Can still be low skill cap champ for new players as well as be a viable pick for the veterans. Now when he can be played sup as well without it being a troll pick. Maybe even jungle can be viable but thats not what I was going for.
I would also say lower the threshold for his ult to execute thus making it more difficult to use effectively adding of more a skill cap to the champ with this kit.