May I suggest a way to balance Tahm Kench?

Tahm Kench is kind of terrible in most ranks of soloqueue, but he can't be buffed because he can effectively QSS+Zhonya a teammate with a press of his W every 20 seconds. Devour has been repeatedly nerfed, but it's still so strong that Tahm needs to be weak (as a whole) or else he will be 100% pick-or-ban in LCS/LEC/etc.

SO I'm suggesting a new approach to balancing his W: Give Devour an on-target cooldown for its use on allies. So the cooldown of W itself will still be 20 seconds (maybe lower?), but he can't eat the same ally more than once every... let's say 120 seconds. This would be a huge nerf to that very specific use of his W, and other aspects of Tahm Kench can then be buffed. Maybe he could get some movement speed, or some base armor/health/MR, more damage/healing, whatever, it's up to you.