Idk how many times but here's one more

Riot make a symbiotic champion!! No not Kai sa she's not the symbiote.

We need a champion that acts as a symbiote that can attach to an ally champion and provide them with buff stats and and secondary abilities (that the symbiote player can use only) the trade off would be a solo bot laner, 1 less champion in the symbiote side. The buff the symbiote gives scales with his stat so if he attaches himself to them at lvl 1 his lvl 1 stats applies and he won't level up until he is detached.

Imagine the symbiote attaching itself to someone and giving them new voice line, skin and visual while in game