New Champion Idea The mischievous ally

The idea is of a support champion that creates a difficulty for an ally but at the same times compensates that with a better buff or by creating a better situation as a trade. The idea of this thread is to trow some concept I thought was cool so don't take anything as set In stone and anyone is encouraged to give your opinion and leave suggestions.

The champion could be ranged and AP

Passive: When Loki hits an enemy with an auto attack it marks him and if an ally auto-attacks the marked enemy it deals bonus damage but also hurts the ally (could be a set amount of true damage also could be that it gives the enemy some move speed instead of damaging the ally)

Q: Silences and ally for x amount of time and gives him bonus move speed

W: Slows an ally and increases it's damage by x% or makes it do some extra magical damage based on the support's AP

E: Damages and ally and gives him a shield (like barrier does) for a greater amount of hp than what was taken for a decent amount of time.

R: Trows an ally as a linear skill shot and when they collide with an enemy champion or as they reach max range deals damage on an area and fears enemies.