Robin hood Soraka
So Soraka is a lil' bit like a communist.
She steals health from enemies and distributes it among teammates evenly.
Riot should create a nice legendary based around making her like a robin hood, taking HP in the visual of money and distributing it to teammates.
I dunno about a particular theme, but just based off of the simple idea of taking money with your Q and redistributing it with your W and R, you could do robin hood, leprechaun... commie raka, whatever.
But your ult can shower teammates with coins, and various other things.
I think it's a nice concept to toy with.