I would remake him into a melee carry.
Passive: Ravenous Hunger
Kog's basic attacks deal 1/2/3% of the target's maximum health in true damage as long as he is not full (resource bar like rage). Each attack fills Kog's belly (resource bar) 4%, tripled when attacking champions and large monsters.
Deteriorates slowly while not in combat for 6 seconds.
Q: Nom!
Kog leaps a short distance to attach into an enemy champion, large or epic monster, gnawing on them for 2 seconds. Deals physical damage. Increases fullness by 10%.
While attached, the target cannot attack Kog (anyone else can attack him though).
W: Gunk Shot
Launches a ball of mucus forward, splashing in a cone behind the first enemy hit. All enemies hit take physical damage and are slowed. Costs 10% fullness.
E: Hunger Pain
When Kog attacks an enemy while below half fullness, he deals bonus damage and recovers extra fullness.
This may be activated while above 50% fullness to use 25% of fullness to launch a ranged attack that snares the target.
R: Bile Barrage
Requires at least 70% fullness. Over the next 5 seconds, Kog spews acidic bile ahead of him. (Think Rumble Flamethrower but straight line ahead). Cannot attack while channeling. Fullness is consumed over the duration. Deals extra damage based on total fullness when cast.