My basic champion with a pet idea. Lets figure it out further together!
I'm thinking an adc who's pet kind of covers the support role. With maybe some CC or maybe engage, but a mixed kit with both some damage from the hero and also that cc or engage, being able to also control the pet's movement like say Morderkaiser's ghost by holding control. It would be a hard af champion to master, but in return you would output massive amounts of damage.
I was also thinking that as a passive, you could get knocked down and take complete control over the pet, replacing the hero's abilities with something else to keep you alive or finish a fight, but instead of a timer before you resurrect, the pet has to come and pick you up within a certain amount of time through a sort of channel or you'll bleed out.
Let's work with this idea in the comments, talking about concepts for the character itself then their abilities as a community.