Probably a stupid idea for Thresh but..

Can we incorporate something for his lantern, the thing that pulls team mates out of their stupid over extensions, either it be to destroy it or have enemies travel on it somehow, he has ZERO risks he can take.

All other supports 'power' (Idk what to call it) has a penalty or a risk

Bard's portal can have enemies travel through it + his ult can affect his team mates in a negative way.

Soraka's heal is punished by sacrificing her own health

Braum's ability to jump infront of team mates makes him the target over the original target.

Blitzcrank can pull in the wrong target and set his team up to get aced.

And just think of the rest of the supports, I think all of them have risks, but Thresh there's nothing you can really do wrong other than not ward or not throwing out your lantern for your team mate, but then again no other support has an ability like that to save your team mate from over extending dozens of times a game.

EDIT: Also all supports have a solid counter in lane phase (Soraka + Ignite, Blitz + Sivir and or support with stun like Leona or Alistar, Braum + Vayne and or Morgana, etc) while the only thing really capable against Thresh is Lulu