The game could use a "Parasitic Champion" whose MO is to stick himself inside his allies...

He'd be a mage with atleast two skillshots to fire around. But his core ability is the ability to drill into an allied unit and remain inside while the allied unit (minion or champion) walks around as though nothing happened.

Then while inside, he could fire his skillshots from within his opponent.

Want to kill the enemy backrow? Attach to an initiator and wait for that initiation to happen. Dying/In danger and need to get away? Dig into an assassin or mobile ADC's body and provide suppressing fire while your ally runs away. His R is, I dunno. Something. Mutate infected host? Pop out of host as an identical clone of the host for a certain duration of time?

His Passive...should have something to do with him being vulnerable in the open, but right at him sticking himself into a friend while firing away.